In a statement, WikiLeaks said Marble was used by the spy agency to "hamper forensic investigators and anti-virus companies from attributing viruses, trojans and hacking attacks to the CIA".

On 7 March and 23 March, two sets of documents were released from the CIA, the first comprising nearly 9000 files and the second a much smaller number.

Marble is used to hide text fragments, which were utilised in malware created by the CIA, from visual inspection.

Graphic: Courtesy WikiLeaks

"When signaturing tools, string obfuscation algorithms (especially those that are unique) are often used to link malware to a specific developer or development shop.

"This framework is intended to help us (AED) to improve upon our current process for string/data obfuscation in our tools."

The WikiLeaks statement said the Marble source code showed that there were test examples in Chinese, Russian, Korean, Arabic and Farsi, apart from English.

"This would permit a forensic attribution double game, for example by pretending that the spoken language of the malware creator was not American English, but Chinese, but then showing attempts to conceal the use of Chinese, drawing forensic investigators even more strongly to the wrong conclusion, --- but there are other possibilities, such as hiding fake error messages," it said.