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BitDefender releases free removal tool for Carberp Trojan

October 2010

Standalone utility available for free download on to protect against growing threat from potent banking Trojan


BitDefender®, an award winning provider of innovative internet security solutions, has announced a free removal tool targeting the Trojan.Downloader.Carberp.A. Building on the technologies implemented in Zeus and Brazilian Bankers, Trojan.Downloader.Carberp.Ahas rapidly obtained its place among a rather exclusive club of banking Trojans. It is designed to intercept, manipulate and steal confidential information a user might send or receive over the internet.

Trojan.Downloader.Carberp.Asnatches details from websites that require log-in sessions over a SSL connection such as online banking services and e-mail providers. Apart from keeping an eye on every service that is important enough to force SSL authentication, Trojan.Downloader.Carberp.A is also instructed to monitor a list of websites containing several e-banking portals.

“Once executed on a computer, Trojan.Downloader.Carberp.A creates a couple of temporary files in the %temp% folder, then copies itself to the Windows Startup folder in order to self implement after every boot or restart,” said Catalin Cosoi, Head of the BitDefender Online Threats Lab. “This approach may seem basic compared to other families of malware that add startup entries to the Registry, however, it is this depreciation that allows Trojan.Downloader.Carberp.A to execute itself on newer operating systems,orrun on users’ accounts that do not have administrative privileges.”

Right after infection, the downloader connects to a C&C server, from which it will download an encrypted configuration file, along with additional fire-power such as plug-ins. This allows Trojan.Downloader.Carberp.A to intercept internet traffic and to kill whatever antivirus it may find on the recently infected computer. It then sends the C&C server a unique ID and uploads a list of currently running processes via a GET request. 

After it has successfully copied itself in the startup folder as either syscron.exe or chkntfs.exe, Trojan.Downloader.Carberp.A hides its presence by using function hooks in ntdll.dll in order to intercept any calls to NtQueryDirectoryFile and ZwQueryDirectoryFile. This means the user cannot see its files when using Windows® Explorer® or the command-line dir query.

Cosoi continues, “Every time a user logs in using SSL-based authentication to gain access to online banking, e-mail and social network accounts Trojan.Downloader.Carberp.A steals their details, before they are encrypted, and sends them to its C&C server over HTTP. By the time the log in request reaches the bank the credentials will already have fallen into the hands of the attackers.”

Trojan.Downloader.Carberp.Aalso targets certain banks in Germany, Denmark, the Netherlands, America and Israel following precise instructions that it receives from the C&C server along with configuration instructions. This sophisticated approach provides a lucrative financial tool designed to steal money from online service customers and SMBs. Trojan.Downloader.Carberp.A is also able to install without administrator privileges, attack systems that run the latest versions of OSs and doesn’t make any changes in the Registry or in critical areas of the operating system.

BitDefender customers have been protected since day zero via generic packer routines already included in the signature database. For those not protected by a BitDefender product, a free removal tool can be downloaded from the Downloads section of

For a full list of BitDefender 2011 features and benefits by product, visit