huntrule

Microsoft BITS Proxy Activity to Uncommon Top-Level Domains

Flags Microsoft BITS-initiated proxy requests to domains using uncommon TLDs.

FreeReviewedSigma · High · v2
Category
proxy
Author
Florian Roth (Nextron Systems), Tim Shelton (SigmaHQ), DRL 1.1
Published
2019-03-07
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution → C2

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies outbound proxy traffic where the client user-agent starts with "Microsoft BITS/" and the destination domain uses an uncommon TLD. Attackers can leverage BITS-like network activity to retrieve content for command-and-control or staging while blending into legitimate updater traffic. The detection relies on proxy logs that capture user-agent strings and the requested destination domain/TLD, excluding known common and specified benign domains.

Reporting behind it

Related detections9 linkedT1071.001 — drag to rearrange
Microsoft BITS Proxy Requests to Uncommon Server IP Hosts
Malicious Encrypted Reverse Shell via Netcat and GPG on Linux
Malicious axios NPM Supply Chain C2 Domain Resolution
Suspicious Reverse Shell via Dev TCP or Netcat
Malicious HarborWatch RAT Command and Control Beacon by User Agent (via proxy)
Suspicious Remote Script Transfer via Bitsadmin (via process_creation)
Suspicious UAT-10608 Credential Harvesting C2 Beacon via HTTP
Malicious BadIIS C2 Communication via lwxatisme User-Agent
Possible PS1Bot C2 Beacon With Drive Serial URI Pattern (via proxy)
Microsoft BITS Proxy Activity to Uncommon Top-Level Domains
Pivot detection · T1071.001 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

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