IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

« Unusual Sudo Activity Unusual Web User Agent »

› › ›

Unusual Web Request

edit

Unusual Web Request

edit

A machine learning job detected a rare and unusual URL that indicates unusual web browsing activity. This can be due to initial access, persistence, command-and-control, or exfiltration activity. For example, in a strategic web compromise or watering hole attack, when a trusted website is compromised to target a particular sector or organization, targeted users may receive emails with uncommon URLs for trusted websites. These URLs can be used to download and run a payload. When malware is already running, it may send requests to uncommon URLs on trusted websites the malware uses for command-and-control communication. When rare URLs are observed being requested for a local web server by a remote source, these can be due to web scanning, enumeration or attack traffic, or they can be due to bots and web scrapers which are part of common Internet background traffic.

Rule type: machine_learning

Machine learning job: packetbeat_rare_urls

Machine learning anomaly threshold: 50

Severity: low

Risk score: 21

Runs every: 15 minutes

Searches indices from: now-45m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://www.elastic.co/guide/en/security/current/prebuilt-ml-jobs.html

Tags:

Elastic
Network
Threat Detection
ML
Command and Control

Version: 5 (version history)

Added (Elastic Stack release): 7.7.0

Last modified (Elastic Stack release): 8.4.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

edit

Web activity that occurs rarely in small quantities can trigger this alert. Possible examples are browsing technical support or vendor URLs that are used very sparsely. A user who visits a new and unique web destination may trigger this alert when the activity is sparse. Web applications that generate URLs unique to a transaction may trigger this when they are used sparsely. Web domains can be excluded in cases such as these. ==== Threat mapping

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
Technique:
- Name: Application Layer Protocol
- ID: T1071
- Reference URL: https://attack.mitre.org/techniques/T1071/

Rule version history

edit

Version 5 (8.4.0 release)

Formatting only

Version 4 (7.12.0 release)

Formatting only

Version 3 (7.10.0 release)

Formatting only

Version 2 (7.9.0 release)

Formatting only

« Unusual Sudo Activity Unusual Web User Agent »