"We are asking anyone interested in cryptology and mathematics to join us in solving the mystery and extracting the hidden payload," said the Moscow-based security company in a blog post Tuesday. "Despite our best efforts, we were unable to break the encryption."
The payload is one of the unknowns of Gauss, a sophisticated spying tool uncovered by Kaspersky last week. According to researchers, Gauss monitors financial transactions with Middle Eastern banks and was built by or backed by one or more governments.
While Kaspersky has figured out that the payload is delivered via USB flash drives - to close the 'air gap' between the Internet and PCs not connected to the Web - it has been stymied in its attempts to decrypt the module, which is encrypted with an RC4 key.
RC4, which was created by RSA Security 25 years ago, is also used in SSL (secure socket layer) to secure communications between websites and browsers.
Kaspersky noted that the decryption key for the payload is generated dynamically by the victimised PC. "[That] prevents anyone except the designated target(s) from extracting the contents of the sections," Kaspersky said today. "It's not feasible to break the encryption with a simple brute-force attack."
Because Gauss has connections to Flame, another cyber snooper that targeted Iranian PCs, and since most experts believe Flame was linked to Stuxnet - the worm discovered in 2010 that sabotaged Iran's nuclear fuel enrichment program - Kaspersky has wondered if Gauss' encrypted payload may contain Stuxnet-like code that targets SCADA (supervisory control and data acquisition) systems.
SCADA systems monitor and control critical industrial processes, ranging from oil refineries and factories to power grids and gas pipelines.
"The resource section [of the encrypted payload] is big enough to contain a Stuxnet-like SCADA-targeted attack code and all the precautions used by the authors indicate that the target is indeed high profile," said Kaspersky.
The security company had previously spelled out other similarities between Gauss and Stuxnet, including the use of a now-patched vulnerability in Windows' shortcuts and the reliance on USB drives to deliver attack code to PCs isolated from the Internet.
In its Tuesday blog post, Kaspersky included the first 32 bytes of encrypted data and hashes from the enigmatic payload.
"If you are a world-class cryptographer or if you can help us with decrypting [this], please contact us by e-mail: [email protected]," said Kaspersky. The company also said it would provide more encrypted data on request.