The file is a zip archive.
The archive contains an ISO file that, once mounted, discloses a classic PE file.
After checking carefully the size of the different files, it was clear that the ZIP archive is 2M but the PE file is much bigger: 400MB! Reminds the “Zip Bomb”?
A malicious very small archive that, once decompressed, is very big and consumes a lot of resources to be unpacked.
From the analysis of the PE file using static analysis techniques (PEstudio) something suspicious comes up
The file has an “overlay” that uses 99% of the file size! And the first bytes are all zeroes.
This overlay starts at offset 0x1B9C00.
Microsoft Windows is very permissive regarding data appended to files.
For example, it’s common to see Word documents containing a macro that extracts a payload located at the end of the file.
Here, the PE file has been altered by appending a lot of zeroes to the code.
That’s the reason why the archive is small.
Packing zeroes is very efficient and produces a small file.
This is a very nice technique to bypass many security controls.
For performance reasons, big files are often skipped or can generate timeouts due to the huge amount of data to analyze.
The PE file is a bitrat sample using the following configuration:
{
“family”: “bitrat”,
“rule”: “Bitrat”,
“c2”: [
“kot-pandora[.]duckdns[.]org:24993”
],
“version”: “1.38”,
“attr”: {
“tor_process”: “tor”,
“communication_password”: “d6723e7cd6735df68d1ce4c704c29a04”
}
}
Sign Up For Threat Alerts
Jul 04, 2023
Rhysida Ransomware RaaS Crawls Out of Crimeware...
The Rhysida ransomware-as-a-service (RaaS) group has gone from a dubious newcomer to a fully-fledged ransomware...
Jun 26, 2023
Operation Magalenha – Long-Running Campaign Pursues Portuguese...
The attackers can steal credentials and exfiltrate users' data and personal information, which can be...
Apr 24, 2023
Lazarus Group Adds Linux Malware to Arsenal...
Researchers have discovered a new campaign conducted by Lazarus, known as "Operation DreamJob," which targets...
Apr 23, 2023
Additional IOCs for 3cx breach
Recently an unexpected malicious activity emanating from a legitimate, signed binary, 3CXDesktopApp was observed.
Apr 23, 2023
Ex-Conti and FIN7 Actors Collaborate with New...
IBM Security X-Force recently discovered a new malware family Analysts have called "Domino," which Analysts...
Apr 20, 2023
AuKill EDR killer malware abuses Process Explorer...
The AuKill tool abuses an outdated version of the driver used by version 16.32 of...
Apr 20, 2023
Fake Chrome updates spread malware
A campaign running since the end of last year is using hacked sites to push...
Apr 20, 2023
QBot using new attack vector in its...
QBot, also known as QakBot, previously operated as a banking trojan and has since transformed...
Apr 20, 2023
CrossLock Ransomware Emerges: New Golang – Based...
The CrossLock ransomware employs the double extortion technique to increase the likelihood of payment from...
Apr 20, 2023
Windows Zero-Day Vulnerability CVE-2023-28252 Exploited by Nokoyawa...
A zero-day vulnerability in the Microsoft Windows system, which also affects Windows 11, has been...
Apr 18, 2023
Additional IOcs for 3cx breach
Recently an unexpected malicious activity emanating from a legitimate, signed binary, 3CXDesktopApp was observed. As...
Apr 18, 2023
Additional IOcs for 3cx breach
Recently an unexpected malicious activity emanating from a legitimate, signed binary, 3CXDesktopApp was observed. As...
Apr 18, 2023
APT36 Expands Interest Within Indian Education Sector
Symantec described UPS in 2016 report as Buckeye (also known as APT3 Gothic Panda UPS...
Apr 17, 2023
ChinaZ DDoS Bot Malware Distributed To Linux...
The ChinaZ DDoS bot malware was discovered targeting Linux systems while a version for Microsoft...
Apr 16, 2023
Resurgence Of The Mexals Cryptojacking Campaign
The Mexals crypto jacking campaign has been in operation since at least 2021 and continues...