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Cisco Secure Firewall - Repeated Malware Downloads

Splunk Security Content

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Summary
The rule titled "Cisco Secure Firewall - Repeated Malware Downloads" is designed to detect malicious activity indicating potential compromise of internal hosts within a network. Specifically, it focuses on identifying instances where an internal host (designated by source IP) downloads malware multiple times in a short period (within five minutes). It leverages logs generated by the Cisco Secure Firewall Threat Defense, filtering `FileEvent` logs that exhibit a `SHA_Disposition` classified as "Malware" and a `FileDirection` indicating a download. The analytic triggers an alert when ten or more such download events occur from the same source IP within the five-minute threshold. This behavior may be indicative of compromised systems retrieving malware for command-and-control operations, preparation for further attacks, or automated processes for distributing malicious content. When retrospective analysis confirms malicious intent, it can signify an ongoing infection, a mechanism for persistence, or operation by a malicious downloader. The implementation requires specific environment settings and the ingestion of logs through the appropriate Splunk Add-on for Cisco Security Cloud. Adequate logging policies must be established to capture these alerts effectively.
Categories
  • Network
  • Endpoint
  • Cloud
Data Sources
  • File
ATT&CK Techniques
  • T1105
  • T1027
Created: 2025-04-09