Tuesday 2023-01-03 and Wednesday 2023-01-04 revealed four Portuguese language emails targetging Brazil. These messages are pushing the same type of Astaroth (Guildma) malware I’ve seen for the past several months.
On an infected Windows host, Astaroth malware is an AutoIt v3 script run by an AutoIt executable. The executable is not inherently malicious on its own. But AutoIt is so closely associated with malware that AutoIt’s website has a wiki article noting legitimate AutoIt binaries are often detected as malicious by antivirus vendors (reference).
I’ve already posted ISC diaries about Astaroth malware in February 2022 and August 2022. Today’s diary presents two email templates from recent waves of malspam, and it briefly reviews artifacts from a persistent infection using AutoIt.
Astaroth malware infects a vulnerable Windows host through AutoIt script. The malicious file is an AutoIt v3 compiled script made persistent through a Windows shortcut under the Startup Menu –> Programs –> Startup directory. The malicious script is run by a legitimate AutoIt executable.
The following are links from the four emails I’ve collected so far in 2023.
Links from first email on Tuesday 2023-01-03:
Links from second email on Tuesday 2023-01-03:
Links from first email on Wednesday 2023-01-04:
Links from second email on Wednesday 2023-01-04:
These URLs are geo-fenced, so they will not provide malware to an English language Windows host from an IP address based in the United States.
A zip archive containing the four emails is available here. Today’s diary is a heads-up for this wave of Astaroth/Guildma activity. I will soon post more technical details about the infection traffic on my blog at www.malware-traffic-analysis.net.
brad [at] malware-traffic-analysis.net
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