Detect Junk Data in Elastic Security
Adversaries may add junk data to protocols used for command and control to make detection more difficult. By appending, prepending, or inserting random or meaningless data into C2 communications, adversaries prevent trivial signature-based detection. Examples include SUNBURST appending junk bytes to HTTP C2, P2P ZeuS adding junk data to UDP peer communications, Downdelph inserting pseudo-random characters between meaningful characters in C2 requests, and GoldMax generating decoy traffic to surround malicious traffic. This technique is primarily a network-level obfuscation method, making it challenging to detect purely through host-based telemetry.
MITRE ATT&CK
- Tactic
- Command and Control
- Technique
- T1001 Data Obfuscation
- Sub-technique
- T1001.001 Junk Data
- Canonical reference
- https://attack.mitre.org/techniques/T1001/001/
Elastic Detection Query
sequence by host.name, process.entity_id with maxspan=10m
[network where process.name : ("powershell.exe","pwsh.exe","cmd.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe","svchost.exe","dllhost.exe") and network.direction == "outbound" and not destination.ip : ("10.0.0.0/8","172.16.0.0/12","192.168.0.0/16","127.0.0.0/8") and destination.port : (80,443,8080,8443,4444,4445,1080,3128)] with runs=5
---
// Alternative: DNS junk label detection
network where event.type == "dns" and dns.question.name : "*" and
length(substring(dns.question.name, 0, indexOf(dns.question.name, "."))) > 20 and
process.name : ("powershell.exe","pwsh.exe","cmd.exe","wscript.exe","cscript.exe","mshta.exe","rundll32.exe","regsvr32.exe")Detects T1001.001 Junk Data C2 obfuscation via two EQL approaches: (1) sequence detection of 5+ repeated outbound connections from suspicious processes to known C2 ports on public IPs indicating beaconing with junk padding, and (2) DNS queries with unusually long first-label subdomains (>20 chars) from suspicious processes suggesting DNS-tunneled C2 with junk data insertion.
Data Sources
Required Tables
False Positives & Tuning
- Software update services (WSUS, SCCM) making high-frequency connections with large payloads to CDN infrastructure
- Security tools performing network scanning or threat intelligence lookups with frequent small packets
- Cloud sync clients (OneDrive, Dropbox) beaconing regularly with consistent payload sizes
- CDN-backed SaaS applications with long subdomain labels for routing (e.g., tenant-id.region.service.example.com)
Other platforms for T1001.001
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1HTTP C2 Simulation with Junk Data Padding
Expected signal: Sysmon Event ID 1: PowerShell process creation with command line containing 'Net.WebClient' and 'UploadString'. Sysmon Event ID 3: Multiple network connection attempts to 127.0.0.1:8080. Security Event ID 4688 (if command line auditing enabled). PowerShell ScriptBlock Log Event ID 4104 showing the full beaconing script.
- Test 2DNS-Based C2 with Junk Subdomain Labels
Expected signal: Sysmon Event ID 22 (DNS Query): Multiple DNS lookup events with QueryName values containing long, random-looking subdomain labels (>20 characters) under c2sim.local. The labels will contain Base64-encoded content with interleaved junk characters. Sysmon Event ID 1 for the PowerShell process creation.
- Test 3Junk Data File Padding Simulation
Expected signal: Sysmon Event ID 11 (File Create): File creation event for junktest_sim.dll in %TEMP% with large file size (~50MB). Sysmon Event ID 1 for the PowerShell process. The file hash (SHA-256) will be recorded in the Sysmon event.
- Test 4Periodic Beaconing with Junk UDP Padding
Expected signal: Sysmon Event ID 3 (Network Connection): UDP connections from powershell.exe to 127.0.0.1:4444 (Sysmon may capture UDP connections depending on configuration). Sysmon Event ID 1 for process creation. Security Event ID 4688 if command line auditing is enabled.
References (15)
- https://attack.mitre.org/techniques/T1001/001/
- https://www.fireeye.com/blog/threat-research/2020/12/evasive-attacker-leverages-solarwinds-supply-chain-compromises-with-sunburst-backdoor.html
- https://arxiv.org/ftp/arxiv/papers/1408/1408.1136.pdf
- https://www.secureworks.com/research/p2p-zeus
- https://www.welivesecurity.com/2016/10/20/anatomy-of-attack-celebrity-malware-downdelph/
- https://www.cisa.gov/sites/default/files/publications/AA22-055A-MuddyWater.pdf
- https://unit42.paloaltonetworks.com/bendybear/
- https://www.crowdstrike.com/blog/observations-from-the-stellarparticle-campaign/
- https://media.defense.gov/2023/May/09/2003218554/-1/-1/0/JOINT_CSA_HUNTING_RUSSIAN_INTELLIGENCE_BOT_SNAKE.PDF
- https://securelist.com/apt10-sophisticated-multi-layered-loader-romabt/101971/
- https://blog.trendmicro.com/trendlabs-security-intelligence/blacktech-espionage-tools-target-east-asia/
- https://www.volexity.com/blog/2024/04/12/zero-day-exploitation-of-unauthenticated-remote-code-execution-vulnerability-in-globalprotect-cve-2024-3400/
- https://www.kaspersky.com/about/press-releases/2021_apt-trends-report-q3-2021
- https://www.microsoft.com/en-us/security/blog/2021/03/04/goldmax-goldfinder-sibot-analyzing-nobelium-malware/
- https://www.welivesecurity.com/2025/02/12/evasive-zipline-group-targets-job-seekers/
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