The detection rule identifies potential malicious activity associated with the MD5 hash c647e85ad77fd9971ba709a08566935d, which may indicate the presence of known or emerging threats. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise early, especially given the low severity rating which may mask more advanced or stealthy adversary tactics.
YARA Rule
rule md5_c647e85ad77fd9971ba709a08566935d {
strings: $ = "fopen(\"cache.php\", \"w+\")"
condition: any of them
}This YARA rule can be deployed in the following contexts:
Scenario: A legitimate system backup process using Veeam Backup & Replication generates a file with the MD5 hash c647e85ad77fd9971ba709a08566935d during a scheduled backup job.
Filter/Exclusion: Check for file paths containing backup, veeam, or vmbackup in the file system event logs.
Scenario: A Windows Task Scheduler job runs a PowerShell script that temporarily creates a file with the same MD5 hash as part of a legitimate configuration update.
Filter/Exclusion: Filter events where the process is initiated by schtasks.exe or where the file path contains task or scheduled.
Scenario: A Docker container running a legitimate application (e.g., Nginx or MySQL) generates a temporary file with the same MD5 hash during runtime.
Filter/Exclusion: Exclude files created within container directories (e.g., /var/lib/docker/) or filter by process names like docker or containerd.
Scenario: A Windows Update or Microsoft Endpoint Manager (MEM) deployment creates a temporary file with the same MD5 hash during software installation.
Filter/Exclusion: Filter events related to wuauclt.exe, setup.exe, or file paths containing WindowsUpdate or Microsoft.
Scenario: A log management tool like Splunk or ELK Stack generates a temporary file with the same MD5 hash during data ingestion or indexing.
Filter/Exclusion: Exclude files in log directories (e.g., /var/log/, C:\ProgramData\splunk\) or filter by process names like splunkd.exe, logstash, or `kibana