Malicious BlueNoroff C2 Communication via cur1-agent User-Agent (via proxy)

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects outbound HTTP traffic carrying the distinctive cur1-agent User-Agent string used by BlueNoroff implants, in which the numeral one replaces the letter l in the word curl. This hardcoded agent string identifies the malware download and C2 requests. No legitimate client emits this User-Agent.

Reporting behind it

Related detections9 linkedT1071.001 — drag to rearrange

Possible GammaSteel C2 Using Spoofed iPhone User Agent

Suspicious PolarEdge Backdoor C2 URL with Module and putdata Command (via proxy)

Suspicious Interlock Backdoor C2 Beacon to init1234 Endpoint (via proxy)

Possible FakeBat Loader Payload Download and C2 URI Patterns

Suspicious HATVIBE C2 Beacon via HTTP PUT to PHP Endpoints (via proxy)

Malicious DDoSia Client C2 Check-In via Fixed User-Agent

Suspicious ctfmon.exe Network Connection to PikaBot C2 Ports

Malicious AddInProcess32 Network Beacon on PureRAT C2 Ports

Malicious Data Exfiltration via curl with Stealer Specific BuildID Header

Malicious BlueNoroff C2 Communication via cur1-agent User-Agent (via proxy)

Pivot detection · T1071.001 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →