The source code for the Carberp financial malware has been leaked online, increasing the risk that other cybercriminals will create their own variants based on it, according to researchers from Russian cybercrime investigations firm Group-IB.

Carberp is a Trojan program used primarily to steal online banking credentials and other sensitive financial information from users. The malware originally targeted users from former Soviet Union states, but the cybercriminals behind it expanded their operations to other regions, like Australia.

Last week, a member of the Carberp gang offered to sell the source code for the malware and its other modules for onlyS$5,000. Group-IB researchers said at the time that the sale was likely the result of an internal conflict within the gang.

According to them, the conflict appears to have since escalated and resulted in the source code, or at least a significant part of it, being leaked online.

On Monday, a Georgian security researcher named Ucha Gobejishvili said on Twitter that the source code for Carberp and its bootkit -- boot rootkit -- module have been leaked. Gobejishvili published a screen shot of a forum post announcing the leak and containing a link to a file hosting site where the password-protected source code archive was allegedly stored.

The file has since been removed from that location, but researchers from Group-IB confirmed that the leak is real.

The archive file contained the full source code for Carberp, but only the partial source code for the bootkit module, said Andrey Komarov, Group-IB's head of international projects, Tuesday via email. He expects the archive to be shared without a password on other cybercrime forums in upcoming days.

This will most likely result in the development of new Carberp variants and Carberp-based banking Trojan programs in the future, as happened with the Zeus financial malware, Komarov said.

The source code for Zeus, one of the most popular online banking Trojan programs to date, was leaked in April 2011, a few weeks after it was put up for sale on the underground market. That leak made a previously expensive crimeware toolkit available free to anyone and also enabled the development of Zeus-based Trojan programs like GameOver and Ice IX.