Suspicious ASPX Webshell Written to IIS inetsrv Directory via file_event

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.003Web Shell
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule detects an fd.aspx file being written under the IIS inetsrv directory, matching the webshell dropped by the hacktivist actors for server access. Web-facing script files appearing in the IIS binaries path are a hallmark of server-side webshell deployment. This supports persistence and remote command execution on internet-facing hosts.

Reporting behind it

Related detections9 linkedT1505.003 — drag to rearrange

Malicious IIS Worker Process Spawning Command Shell for Webshell Reconnaissance (via process_creation)

Malicious Command Shell Spawned by SQL Server via Process Creation (via process_creation)

Suspicious PHP Webshell Access with Hardcoded Key

Suspicious IIS Configuration Reconnaissance via Appcmd (via process_creation)

Malicious ManagementMailboxPicker Webshell Written by Diplomatic Specter

Malicious MOVEit human2 Webshell File Creation via file_event

Suspicious Double-Extension Web Shell Upload via Nagios XI Custom Includes

Suspicious Malicious WAR Deployment via GlassFish Admin Console

Suspicious JSP Webshell Compiled Class Creation in Web Application Work Directory

Suspicious ASPX Webshell Written to IIS inetsrv Directory via file_event

Pivot detection · T1505.003 · 9 related

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

Full detection rule

Unlock this rule to view and copy it

The detection logic is included with a plan. Everything else — context, mappings and implementation details — stays free on this page.

Sign in for 3 free unlocks

Signing in gives you 3 unlocks to spend on any rule in the library. No card, and they do not expire.

Also included

Unlocked rules convert on this page — to Splunk SPL or Splunk — Raw Index SPL or Microsoft Sentinel KQL or Microsoft Sentinel ASIM ASIM KQL or Microsoft Defender XDR KQL or Elastic Security KQL or Elastic Security Lucene or Elastic Security ES|QL or CrowdStrike Falcon CQL or SentinelOne PowerQuery or Palo Alto Cortex XDR XQL or Carbon Black Cloud Platform Search or Carbon Black EDR Process Search or Google Security Operations UDM Search or IBM QRadar AQL or Sumo Logic Cloud SIEM Rules expression or Rapid7 InsightIDR LEQL or Graylog Search or OpenSearch Lucene or OpenSearch PPL PPL or Grafana Loki LogQL or SQLite SQL or Zircolite SQLite — with the log-source profile the engine picked, the field map it used, and everything it could not express. Converting a rule you have unlocked costs no further credit.

See it run on a free rule →Convert your own rule →