Sigma rule: Suspicious C2 Activities

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-d9288a417b8b, updated 2021-11-27T00:00:00.000Z.

Rule

Title
Suspicious C2 Activities
Status
test
Level
medium
Author
Marie Euler
Date
2020-05-18
Modified
2021-11-27
File
rules/linux/auditd/lnx_auditd_susp_c2_commands.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects suspicious activities as declared by Florian Roth in its 'Best Practice Auditd Configuration'.
This includes the detection of the following commands; wget, curl, base64, nc, netcat, ncat, ssh, socat, wireshark, rawshark, rdesktop, nmap.
These commands match a few techniques from the tactics "Command and Control", including not exhaustively the following; Application Layer Protocol (T1071), Non-Application Layer Protocol (T1095), Data Encoding (T1132)

Log source

product
linux
service
auditd
definition
Required auditd configuration: -w /usr/bin/wget -p x -k susp_activity -w /usr/bin/curl -p x -k susp_activity -w /usr/bin/base64 -p x -k susp_activity -w /bin/nc -p x -k susp_activity -w /bin/netcat -p x -k susp_activity -w /usr/bin/ncat -p x -k susp_activity -w /usr/bin/ss -p x -k susp_activity -w /usr/bin/netstat -p x -k susp_activity -w /usr/bin/ssh -p x -k susp_activity -w /usr/bin/scp -p x -k susp_activity -w /usr/bin/sftp -p x -k susp_activity -w /usr/bin/ftp -p x -k susp_activity -w /usr/bin/socat -p x -k susp_activity -w /usr/bin/wireshark -p x -k susp_activity -w /usr/bin/tshark -p x -k susp_activity -w /usr/bin/rawshark -p x -k susp_activity -w /usr/bin/rdesktop -p x -k susp_activity -w /usr/local/bin/rdesktop -p x -k susp_activity -w /usr/bin/wlfreerdp -p x -k susp_activity -w /usr/bin/xfreerdp -p x -k susp_activity -w /usr/local/bin/xfreerdp -p x -k susp_activity -w /usr/bin/nmap -p x -k susp_activity (via https://github.com/Neo23x0/auditd/blob/ddf2603dbc985f97538d102f13b4e4446b402bae/audit.rules#L336)

Detection

selection:
    key: 'susp_activity'
condition: selection

False positives (as the rule lists them)

  • Admin or User activity

Tags

  • attack.command-and-control

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/linux/auditd/lnx_auditd_susp_c2_commands.yml

Sources and licences

  • SigmaHQ

    "Suspicious C2 Activities" by Marie Euler (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/linux/auditd/lnx_auditd_susp_c2_commands.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Suspicious C2 Activities",
entity page, dataset version ref-d9288a417b8b, updated 2021-11-27T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/f7158a64-6204-4d6d-868a-6e6378b467e0 (accessed 2026-11-03).
Underlying source: SigmaHQ rule f7158a64-6204-4d6d-868a-6e6378b467e0, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.