A Zip Bomb to Bypass Security Controls and Sandboxes

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

Loading...
Threats Icon

Aug 08, 2022

RapperBot – new evolving malware

FortiGuard Labs has been tracking a rapidly evolving IoT malware family known as "RapperBot". This...

Threats Icon

Aug 04, 2022

Google Drive And Dropbox Used By APT29...

Cloaked Ursa (aka: APT29) has been targeting governmental entities in several countries with spear-phishing campaigns...

Threats Icon

Aug 03, 2022

Manjusaka: A Chinese sibling of Sliver and...

Cisco Talos recently discovered a new attack framework called "Manjusaka" being used in the wild...

Threats Icon

Aug 03, 2022

macOS Targeted With The CloudMensis Multi-Staged Malware

ESET researchers discovered a previously unknown macOS backdoor that spies on users of the compromised...

Threats Icon

Aug 01, 2022

Attackers Target Ukraine With GoMet Backdoor

Since the Russian invasion of Ukraine began, Ukrainians have been under a nearly constant barrage...

Threats Icon

Jul 31, 2022

Untangling KNOTWEED: European private-sector offensive actor using...

The Microsoft Threat Intelligence Center (MSTIC) and the Microsoft Security Response Center (MSRC) found a...

Threats Icon

Jul 31, 2022

Untangling KNOTWEED: European private-sector offensive actor using...

The Microsoft Threat Intelligence Center (MSTIC) and the Microsoft Security Response Center (MSRC) found a...

Threats Icon

Jul 26, 2022

EvilNum Targets Cryptocurrency, Forex, Commodities

Proofpoint Threat Research observed the group Proofpoint calls TA4563 targeting various European financial and investment...

Threats Icon

Jul 25, 2022

Lightning Framework: New Undetected “Swiss Army Knife”...

Lightning is a previously undocumented and undetected Linux threat. Lightning is a modular framework we...

Threats Icon

Jul 24, 2022

Redeemer Ransomware

Redeemer 2.0 Being Distributed Via Affiliate Program Cyble Research Labs has constantly been tracking emerging...

Threats Icon

Jul 21, 2022

Cobalt Strikes again: UAC-0056 continues to target...

The Malwarebytes Threat Intelligence team recently reviewed a series of cyber attacks against Ukraine that...

Threats Icon

Jul 20, 2022

Trello From the Other Side: APT29 Phishing...

Beginning mid-January 2022, Mandiant detected and responded to an APT29 phishing campaign targeting a diplomatic...

Threats Icon

Jul 18, 2022

New OrBit Linux Malware That Hijacks Execution...

New and entirely undetected Linux threat dubbed OrBit, signally a growing trend of malware attacks...

Threats Icon

Jul 18, 2022

North Korean threat actor targets small and...

A group of actors originating from North Korea that Microsoft Threat Intelligence Center (MSTIC) tracks...

Threats Icon

Jul 13, 2022

ChromeLoader – New Stubborn Malware Campaign

A new browser hijacker/adware campaign named ChromeLoader (also known as Choziosi Loader and ChromeBack) was...