Bank trojan targets users of Bitcoin exchange Mt Gox

Hackers are spreading malware that hijacks a victim’s browser and redirects it to a phishing page for the Bitcoin exchange Mt. Gox.

Brazilian hackers on the hunt for banking credentials are now targeting Bitcoin owners with a trick that sends victims to a phishing page when they enter the correct URL for Mt Gox, the online exchange that claims to account for 80 per cent of all Bitcoin trade.

The phishing page for Mt. Gox was discovered earlier this month by Steven K, a security researcher for the cyber crime blog XiliBox.

The malware that pushes victims to the site is a Java applet that manipulates a browser’s proxy server configuration settings, according to Kaspersky Lab researcher Fabio Assolini.

Hackers have planted a malicious and hidden iframe on compromised websites that loads a Java applet "update.pac" via a phishing site "".

“The iframe loads a malicious Java applet prepared to change the proxy configuration on web browser such as IE and Firefox. The URL used in the attack points to a file called update.pac,” said Assolini.

The file is only detected by two of 46 antivirus products, however the site is detected as a phishing page by 10 products, according to Virus Total.

The hackers are not exploiting a browser flaw, but are rather abusing a feature in all browsers that network administrators can use to alter where a browser automatically goes when it attempts to fetch a certain URL.

Proxy auto-configuration (PAC) files contain JavaScript functions that let admins customise where a browser goes for a list of URLs, however hackers have found the feature useful in phishing campaigns.

Brazilian banker trojans have previously used PAC files to redirect victims to a custom phishing page when they attempt to visit their bank’s site. The file contains a list of target banks and a corresponding phishing page for each site.

The Mt. Gox element of the malware that Kaspersky labels is part of a wider campaign aimed at customers of American Express and Brazilian bank Bradesco amongst others.

The malware redirects the victim to the domain, which will not resolve unless the machine is infected, according to Assolini.

“The goal is clear: redirect victims to a fake page of to steal credentials, and consequently, some bitcoins. If you’re a regular visitor to, we recommend activating the two-factor authentication in your account so as not to fall victim to this kind of attack.”

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