Online PDF converters provide efficient conversions of documents from one file format to another, and millions of individuals and businesses use these services to do so. However, this free service also poses significant cybersecurity risks despite its convenience. According to the Federal Bureau of Investigation's (FBI) advisory issued a month ago, cybercriminals have been increasingly exploiting online file conversion platforms to spread malware to consumers and businesses.
As a result of the threat actor's embedding of malware into seemingly legitimate file conversion processes, data, financial information, and system security are being put at serious risk as a result. As the popularity of these services grows, so does the potential for widespread cyberattacks. Thus, users must exercise heightened caution when choosing tools for managing digital assets online and adhere to best practices when protecting their digital assets when selecting online tools.
Among the many concerns regarding cyber threats that have recently erupted in the form of a report by a cybersecurity firm, a sophisticated malware campaign has been discovered that takes advantage of counterfeit PDF-to-DOCX conversion platforms to compromise users and expose their data.
Using highly capable malware, this campaign can steal a wide variety of sensitive data, such as passwords, cryptocurrency wallets, and other confidential personal data from websites.
This threat emerged in a matter of time following a public advisory issued by the Denver division of the FBI, warning the public of the increase in malicious file conversion services being used to spread malware. As a result of the findings of cybersecurity firm, cybercriminals have meticulously developed deceptive websites like candyxpdf[.]com and candyconverterpdf[.]com, which imitate the appearance and functionality of the legitimate file conversion service pdfcandy.com, to exploit the public.
PDFcandy.com's original platform, well-known for its comprehensive PDF management tools, is reportedly attracting approximately 2.8 million visitors per month, making it a prime target for threat actors seeking to exploit its user base as a means of gaining a competitive advantage. A significant aspect of the platform is the significant number of users based in India, where 19.07% of its total traffic comes from, equivalent to approximately 533,960 users per month.
As a result of this concentration, cybercriminals operating fraudulent websites have an ample pool of potential victims to exploit.
According to data collected in March of 2025, the impersonating sites fetched approximately 2,300 and 4,100 visitors from unsuspecting users, indicating an early but concerning growth among those unaware of the impersonating sites.
A growing number of sophisticated threats are being employed by threat actors, as indicated by these developments. They emphasize the need for heightened user vigilance and strong cybersecurity measures at all levels.
An FBI report has highlighted the growing threat posed by fraudulent online document conversion tools, which have been issued by the Federal Bureau of Investigation (FBI).
This is in response to an alert recently issued by the FBI Denver Field Office, which warns of the increasing use of these seemingly benign services not just by cybercriminals to steal sensitive user information, but also to install ransomware on compromised devices, in more severe cases. As a result of an alarming rise in reports concerning these malicious platforms, the agency issued a statement in response.
There has been an increase in the number of deceptive websites offering free document conversion, file merging, and download services by attackers, as indicated in the FBI's advisory. It is important to note that although these tools often perform the file conversions promised, such as converting a .DOC file into a. A PDF file or merging multiple .JPG files into one.PD, the FBI warns that the final downloaded files may contain malicious code.
It can be used by cybercriminals to gain unauthorised access to the victim’s device, thereby putting the victim in an extremely dangerous position in terms of cybersecurity.
The agency also warns that documents that are uploaded to these platforms may contain sensitive information such as names, Social Security numbers, cryptocurrency wallet seeds and addresses, passphrases, email credentials, passwords, and banking information, among others.
In addition to identity theft, financial fraud, and subsequent cyberattacks, such information can be exploited to steal identities, commit financial fraud, or commit further cyberattacks.
The FBI Denver Field Office confirmed in a report that complaints were on the rise, with even the public sector reporting incidents recently in the metro Denver area.
During her remarks, Vicki Migoya, FBI Denver Public Affairs Officer, pointed out that malicious actors often use subtle methods to deceive users. For instance, malicious actors alter a single character in a website URL or substitute suffixes such as “INC” for “CO” to create a domain name that is very similar to legitimate ones. Additionally, as search engine algorithms continue to prioritise paid advertisements, some of which may lead to malicious sites, users searching for “free online file converters” should be aware of this warning, as they may be particularly vulnerable to threats.
Despite the FBI's decision to withhold specific technical details so as not to alert threat actors, the agency confirmed that such fraudulent tools remain a preferred method for spreading malware and infecting unsuspecting computer users. Upon investigating the malware campaign further, the FBI discovered that the deceptive methods employed by the fraudulent websites to compromise users were deceptively deceptive.
When a user visits such websites, he or she is required to upload a PDF document to convert it into Word format.
It is then shown that the website has a loading sequence that simulates a typical conversion process, to give the impression that the website is legitimate. Additionally, the site presents users with a CAPTCHA verification prompt as well, a method of fostering trust and demonstrating that the website complies with common security practices seen on reputable websites. Nevertheless, as soon as the user completes the CAPTCHA, they are deceptively instructed to execute a PowerShell command on their system, which is crucial to begin the malware delivery process.
After the user clicks on Adobe. A zip file is then installed on the user's device and contains a malware infection called ArechClient, a family of information-stealing malware which is associated with the Sectopratt malware family. Known to be active since 2019, this particular strain of malware is specifically designed to gather a wide range of sensitive data, including saved usernames and passwords, as well as cryptocurrency wallet information and other important digital assets.
Some of these malicious websites have been taken offline by authorities in recent weeks, but a recent report by a known cybersecurity firm states that over 6,000 people have visited these websites during the past month alone. Clearly, cybercriminals are actively exploiting this vulnerability at scale and with a high degree of frequency. Users must verify the legitimacy of any online conversion service they use due to the increasing sophistication of such attacks.
During the time of a web-based search, it is essential to make sure that the website is legitimate, not a phoney copy that is being manipulated by hackers. If an unknowing compromise has taken place on a device, action must be taken immediately, such as isolating it and resetting all the associated passwords, to minimise any damage done. For sensitive file conversions, cybersecurity experts recommend using trustworthy offline tools whenever possible to reduce their exposure to online attacks.
As cyber threats to online file conversion services have become increasingly sophisticated, users must be increasingly vigilant and security-conscious when conducting digital activities. For all individuals and organisations to feel comfortable uploading or downloading any files to a website, they are strongly encouraged to check for its authenticity before doing so.
Among the things that users should do is carefully examine URLS for subtle anomalies, verify a secure connection (HTTPS), and favour trusted, well-established platforms over those that are less-known or unfamiliar.
In addition, users should avoid executing any unsolicited commands or downloading unexpected files, even when the website seems to be a genuine one.
It is crucial to prioritise the use of offline, standalone conversion tools whenever possible, especially when dealing with sensitive or confidential documents. If it is suspected that a compromised device or computer has been compromised, immediate steps should be taken to isolate the affected device, reset all relevant passwords, and contact cybersecurity professionals to prevent a potential breach from taking place.
In the age of cybercriminals who are constantly enhancing their tactics, fostering a culture of proactive cyber awareness and resilience is no longer optional, but rather a necessity. To combat these evolving threats, it will be imperative for organisations to consistently train staff, update security protocols, and effectively use best practices. Users need to exercise greater caution and make informed decisions to prevent themselves as well as their organisations from the far-reaching consequences of cyberattacks in the future.
