A mistake by a suspected Russian-speaking cybercriminal group allowed a security vendor to peep on a campaign that stole login credentials for hundreds of thousands of online bank accounts.
In a new report, Proofpoint said it found a large number of WordPress websites that had been compromised to perform a drive-by download of Qbot, also known as Qakbot, a malicious software program.
Proofpoint analyzed the malware and found an unprotected control panel on a server used by the gang to control the computers, a dumb but not uncommon mistake.
The control panel yielded a wealth of information about the malware campaign, which Proofpoint said collected 800,000 credentials for online bank accounts, many of which were at five of the largest U.S. banks and some in Europe.
Fifty-two percent of the compromised computers were running Windows XP, "a figure that is at once unsurprising -- considering that support for Windows XP, including patches, ended in April 2014," according to the report.
Most of those computers were running Internet Explorer, "which is to be expected given both the size of the Internet Explorer install base and the number and variety of exploits available for this browser," the report said.
Qbot uses a technique called browser "hooking" to steal banking credentials. Online banking sessions are encrypted using SSL/TLS (Secure Sockets Layer/Transport Security Layer) encryption, but Qbot hooks into the browser to read the content after the browser has decrypted the traffic.
Users are infected after they visit a WordPress site or other websites that have been rigged to deliver an attack. Websites running WordPress' platform are often sought after by hackers due to its wide use and because it is not uncommon to find unpatched versions of it running.
"When end users browse the websites compromised by the attackers, the scripts that the attackers added to the compromised site's page will cause the visiting browsers to ultimately load and run unwanted software in a manner that is completely transparent to the end user," the report said.
In addition to stealing online banking credentials, the attackers also appear to be making money from the hacked computers in other ways.
The Qbot malware also has a module called "SocksFabric" for a tunneling network. That network can be rented to other cybercriminals who can use the hacked computers as proxies to shuffle their own data around or mask their activity.
Proofpoint wrote it isn't possible to see how much the group has netted, but the large number of compromised accounts would indicate that "this cybercrime group has the potential for tremendous profits."
Send news tips and comments to [email protected] Follow me on Twitter: @jeremy_kirk