CloudSEK’s Security Research team, a sophisticated cyberattack leveraging malicious online PDF converters has been demonstrated to target individuals and organizations globally.
This attack, previously hinted at by the FBI’s Denver field office, involves the distribution of potent malware, known as ArechClient2, which is a variant of the harmful SectopRAT family of information stealers.
The Deception Unveiled
The attackers ingeniously crafted fake websites, candyxpdf[.]com and candyconverterpdf[.]com, which arecl startlingly similar to the user experience of pdfcandy.com, a legitimate PDF conversion service.
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These deceptive platforms lure users with the promise of converting PDF files into DOCX format.
However, this promise serves as a bait to exploit common file conversion needs to initiate an attack vector:
- Visual Deception: The fake sites replicate the branding, logo, and overall design of pdfcandy.com, making them appear trustworthy to unsuspecting users.
- User Interaction: Once a user proceeds with file conversion, a series of manipulated interactions are initiated:
- Simulated Processing: A sequence mimicking file processing reassures users of the site’s functionality.
- Fake Captcha: An abrupt captcha verification prompt is designed not only to legitimize the site but also to expedite the attack by hastening user actions.
- PowerShell Execution: Users are tricked into running a PowerShell command, the linchpin in the cyber attack’s chain.
Technical Manipulation
The deceptive process culminates with the download of “adobe.zip” from bind-new-connect[.]click, a domain notorious for distributing ArechClient2 malware.
The payload, hosted on the IP address 172[.]86[.]115[.]43, contains an archive that expands to a “SoundBAND” folder with an executable “audiobit[.]exe”.
According to the Report, this execution triggers a multi-stage attack, employing cmd[.]exe and MSBuild[.]exe to install the information stealer stealthily.
To defend against these advanced threats, consider the following:
| Category | Action |
|---|---|
| Rely on Verified Tools | Always use file conversion tools from their official websites rather than searching for “free converters.” |
| Technical Safeguards | 1. Keep anti-malware software updated and scan all downloads. |
| 2. Implement endpoint detection and response (EDR) solutions. | |
| 3. Use DNS-level filters to block known malicious domains. | |
| 4. Check file integrity beyond just examining extensions. | |
| User Training | Educate users to spot red flags like PowerShell execution requests or minor URL variations. |
| Response to Compromise | 1. Isolate any potentially compromised device immediately. |
| 2. Change all passwords using a secured, non-compromised device. | |
| 3. Alert financial institutions and report the incident to relevant authorities. |
This detailed expose on the malicious PDF converter scheme underscores the sophistication of today’s cyber attackers.
By maintaining vigilance, employing robust security measures, and fostering an informed user base, one can significantly mitigate the risk of falling victim to such intricate cyber threats.
Indicators of Compromise (IOC)
| IOC | Description |
|---|---|
| candyxpdf[.]com | Malicious domain |
| candyconverterpdf[.]com | Another malicious domain |
| bind-new-connect[.]click | Known malware distributor |
| 172[.]86[.]115[.]43 | Malicious IP hosting “adobe.zip” |
| “adobe[.]zip” | Malicious payload archive |
| “audiobit[.]exe” | Malicious executable inside “adobe.zip” |
| 72642E429546E5AB207633D3C6A7E2E70698EF65 | Hash for “adobe.zip” |
| 51de0b104e9ced3028a41d01dedf735809eb7f60888621027c7f00f0fcf9c834 | Hash for “audiobit[.]exe” |
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