Cyber Security News

Hackers Use DLL Side-Loading to Deploy Malicious Python Code

A recent discovery by Xavier Mertens, a senior handler at the Internet Storm Center, has highlighted a sophisticated attack where hackers utilize DLL side-loading to deploy malicious Python code.

This technique involves tricking an application into loading a malicious DLL instead of a legitimate one, allowing attackers to execute malicious code while evading detection by security tools.

The Attack Vector

The attack begins with a ZIP archive named “Hootsuite (1).zip,” which contains a file named Hootsuite.exe disguised as a PDF reader.

 Python Code Python Code
behavior of the PDF reader

This executable is a copy of the old Haihaisoft PDF reader, known to have a DLL side-loading vulnerability. When executed from a normal directory, it functions as expected.

However, when run from the directory extracted from the ZIP archive, it loads a malicious msimg32.dll instead of the legitimate Microsoft version.

This malicious DLL is significantly larger than the official one, likely to avoid detection by security tools due to performance considerations.

Upon execution, the PDF reader’s behavior changes dramatically, as confirmed through debugging.

The attack involves unpacking and installing a Python environment, fetching a Python bot, and executing it using a renamed “synaptics.exe” to bypass security rules that monitor for suspicious process names.

Persistence is achieved by adding a registry entry that runs a batch script at startup, ensuring the malware remains active even after the system restarts.

Evasion Techniques and Persistence

The attackers employed several evasion techniques, including renaming the Python executable to “synaptics.exe” to avoid detection by simple security rules.

Additionally, they used a Base64-encoded string to implement persistence, which involves creating a batch script that runs at startup.

According to the Report, this script is encoded and decoded using certutil, a legitimate Windows tool, to further evade detection.

The use of a decoy PDF file, which is not malicious, serves as a distraction, opening in the default system viewer to maintain the illusion of legitimacy.

This incident underscores the growing sophistication of attacks leveraging DLL sideloading, a technique that exploits Windows’ DLL loading behavior to execute malicious code within the context of legitimate applications.

It highlights the need for robust security measures to protect against such threats, particularly in environments where Python and other scripting languages are used extensively.

Are you from SOC/DFIR Teams? – Analyse Malware Incidents & get live Access with ANY.RUN -> Start Now for Free.

Aman Mishra

Aman Mishra is a Security and privacy Reporter covering various data breach, cyber crime, malware, & vulnerability.

Recent Posts

Gunra Ransomware’s Double‑Extortion Playbook and Global Impact

Gunra Ransomware, has surfaced as a formidable threat in April 2025, targeting Windows systems across…

5 hours ago

Hackers Exploit 21 Apps to Take Full Control of E-Commerce Servers

Cybersecurity firm Sansec has uncovered a sophisticated supply chain attack that has compromised 21 popular…

5 hours ago

Hackers Target HR Departments With Fake Resumes to Spread More_eggs Malware

The financially motivated threat group Venom Spider, also tracked as TA4557, has shifted its focus…

5 hours ago

RomCom RAT Targets UK Organizations Through Compromised Customer Feedback Portals

The Russian-based threat group RomCom, also known as Storm-0978, Tropical Scorpius, and Void Rabisu, has…

6 hours ago

Hackers Use Pahalgam Attack-Themed Decoys to Target Indian Government Officials

The Seqrite Labs APT team has uncovered a sophisticated cyber campaign by the Pakistan-linked Transparent…

6 hours ago

LUMMAC.V2 Stealer Uses ClickFix Technique to Deceive Users into Executing Malicious Commands

The LUMMAC.V2 infostealer malware, also known as Lumma or Lummastealer, has emerged as a significant…

6 hours ago