214. That's How Adversaries Sanitize Logs

Hello everyone!

Adversaries often delete logs. But in some cases we can see more sophisticated approach. For example, they can sanitize the logs.

Let's look at the report on CL-STA-0969. They used utmpdump to dump the contents of the wtmp log file:

utmpdump /var/log/wtmp >/var/log/wtmp.file

Then they used sed to remove lines containing their IP address:

sed -i '/<IP Address>/d' /var/log/wtmp.file

And finally utmpdump again:

utmpdump -r /var/log/wtmp.file > /var/log/wtmp

So, for example, we can search for suspicious utmpdump executions:

event_type: "processcreatenix"

AND

proc_file_path: "utmpdump"

AND

cmdline: "wtmp"

See you tomorrow!

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