FBI warns about document conversion sites spreading malware

Online document conversion sites have been a lifesaver, whether you need to turn a PDF into an editable document, convert a PPT into a PDF or open a lesser-known file format. 

Most of these sites are free and deliver quick results, but many also pose serious privacy risks. When you upload your documents, you’re essentially handing them over to a service with no obligation to protect them. 

Now, the FBI is warning that some free online document converters go a step further by loading malware onto your computer. These malicious sites complete the conversion but also silently install malware on your device.

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What you need to know

The FBI Denver Field Office is warning about a scam involving free online document converter tools that cybercriminals are using to spread malware. These malicious tools can lead to serious incidents, including ransomware attacks.

Hackers worldwide are exploiting any type of free document converter or downloader tool to carry out this scheme. The scam may involve websites that promise to convert files, such as turning a .doc into a .pdf, or tools that claim to merge multiple images into a single document. Some even pose as MP3 or MP4 downloaders. While these tools perform the advertised task, the resulting file may contain hidden malware, giving attackers access to the victim’s computer.

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These tools can also extract sensitive information from submitted files, including personal details like Social Security numbers, dates of birth and phone numbers. They may also harvest banking details, cryptocurrency data such as seed phrases and wallet addresses, as well as email addresses and passwords.

“Unfortunately, many victims don’t realize they have been infected by malware until it’s too late, and their computer is infected with ransomware or their identity has been stolen,” the feds note.

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FBI suggests steps to protect yourself

The FBI advises you to pause, slow down and think carefully before taking any actions online. To reduce the risk of malware infections, keep your antivirus software updated and scan any downloaded files before opening them, the security service noted. 

A strong antivirus software safeguards you from malicious links that install malware, potentially accessing your private information. This protection can also alert you to phishing emails and ransomware scams, keeping your personal information and digital assets safe. Get my picks for the best 2025 antivirus protection winners for your Windows, Mac, Android and iOS devices.

The FBI Denver Field Office also urges anyone who has fallen victim to or encountered this scam to report it to the FBI’s Internet Crime Complaint Center at www.ic3.gov.

“The best way to thwart these fraudsters is to educate people so they don’t fall victim to these fraudsters in the first place,” said FBI Denver Special Agent in Charge Mark Michalek. “If you or someone you know has been affected by this scheme, we encourage you to make a report and take actions to protect your assets. Every day, we are working to hold these scammers accountable and provide victims with the resources they need.”

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Additional ways to stay safe from malicious document conversion tools

1. Use official conversion tools: Instead of relying on random online tools, download and use reputable document conversion software provided by reputable companies like Adobe Acrobat, LibreOffice or Microsoft Office. These programs let you convert files securely without exposing your data to potential threats.

2. Check the website’s reputation: Before using an online converter, research the site. Look for reviews and see if cybersecurity forums or sources have flagged it as unsafe. If the site lacks basic security measures, avoid it.

3. Avoid downloading executable files: If an online document converter provides an .exe, .bat or .scr file instead of a standard document format, do not download or run it. Legitimate converters should only generate files like .pdf, .docx or .png, not executables that could contain malware.

4. Scan files after conversion: Even if you use a trusted converter, always scan the converted file with up-to-date strong antivirus software before opening it.

5. Check file permissions: After conversion, verify that the new file doesn’t have unexpected permissions or properties that could indicate malware.

6. Create backups and enable ransomware protection: Regularly back up important documents on an external drive or a secure cloud service. Some security suites, like Microsoft Defender, offer ransomware protection features that prevent unauthorized changes to your files.

7. Be cautious of browser extensions: Avoid installing browser extensions for file conversion, as these can often be browser hijackers or adware.

8. Consider paid services: If you frequently need to convert files, invest in a reputable paid service that offers better security and privacy protection.

9. Use cloud-based solutions: Consider using cloud-based productivity suites that offer built-in conversion tools, reducing the need for third-party converters.

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Kurt’s key takeaway

The convenience of free online tools often blinds us to the risks they carry. Many users assume that if a website looks professional or ranks high on Google, it must be safe. Cybercriminals understand this mindset and take full advantage of it.

The real issue is not just malware-laced converters but the habit of trading security for convenience without a second thought. The internet is filled with services that appear free but come at the hidden cost of stolen data, financial fraud or compromised devices. Instead of trusting every tool that offers an easy solution, it is important to think critically about what we are giving away whenever we upload a file or click a download button.

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