Techniques
Sample rules
Cisco Secure Firewall - Repeated Malware Downloads
- source: splunk
- technicques:
- T1105
- T1027
Description
The following analytic detects repeated malware file downloads initiated by the same internal host (src_ip) within a short time window. It leverages Cisco Secure Firewall Threat Defense logs and identifies FileEvent events with a SHA_Disposition of “Malware” and FileDirection set to “Download”. If ten or more such events occur from the same host within five minutes, this analytic will trigger. This activity may indicate the host is compromised and repeatedly retrieving malicious content—either due to command-and-control, malware staging, or automation. If confirmed malicious, this behavior may represent an infection in progress, persistence mechanism, or a malicious downloader.
Detection logic
`cisco_secure_firewall` EventType=FileEvent SHA_Disposition="Malware" FileDirection="Download"
| lookup cisco_secure_firewall_filetype_lookup Name as FileType OUTPUT Description
| bin _time span=5m
| stats count min(_time) as firstTime max(_time) as lastTime
values(uri) as uri
values(ClientApplication) as ClientApplication
values(app) as app
values(file_hash) as file_hash
values(SHA_Disposition) as SHA_Disposition
values(file_name) as file_name
values(ThreatName) as ThreatName
values(dest) as dest
values(dest_port) as dest_port
by src_ip FileDirection FileType Description
| where count >= 10
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| table firstTime lastTime src_ip dest dest_port FileDirection FileType Description uri file_name file_hash app ClientApplication ThreatName SHA_Disposition
| `cisco_secure_firewall___repeated_malware_downloads_filter`