Chafer malware C2 URLs with /asp.asp?ui= pattern over HTTP 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 matches HTTP proxy requests whose URL path contains /asp.asp?ui=. Such a pattern is used to receive data from command-and-control infrastructure, making it a high-signal indicator for suspicious outbound communications. It relies on proxy telemetry that includes the full requested URI (c-uri) for each HTTP request.

Reporting behind it

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Chafer malware C2 URLs with /asp.asp?ui= pattern over HTTP proxy

Pivot detection · T1071.001 · 9 related

Changelog

v5

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
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.

chafer-malware-c2-http-requests-matching-asp-asp-ui-pattern-fb502828

title: Chafer malware C2 URLs with /asp.asp?ui= pattern over HTTP proxy
id: 249207b2-3d50-4850-b41d-b4b9d6307ac9
status: test
description: This rule matches HTTP proxy requests whose URL path contains /asp.asp?ui=. Such a pattern is used to receive data from command-and-control infrastructure, making it a high-signal indicator for suspicious outbound communications. It relies on proxy telemetry that includes the full requested URI (c-uri) for each HTTP request.
references:
  - https://securelist.com/chafer-used-remexi-malware/89538/
  - https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2019/Malware/Chafer/proxy_malware_chafer_url_pattern.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2019-01-31
modified: 2024-02-15
tags:
  - attack.command-and-control
  - attack.t1071.001
  - detection.emerging-threats
logsource:
  category: proxy
detection:
  selection:
    c-uri|contains: /asp.asp\?ui=
  condition: selection
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: fb502828-2db0-438e-93e6-801c7548686d
    type: derived

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