Rupert Murdoch has taken to Twitter again to lash out at Australian publisher Fairfax, with the News Corporation founder saying only "crazy" people would trust the piracy allegations made by one of his rival's titles against NDS. Murdoch's latest outburst late on Thursday coincided with NDS publishing a letter to Fairfax's Australian Financial Review, accusing the newspaper of a "shocking manipulation" of evidence in a series of articles accusing the former News Corp encryption subsidiary of encouraging piracy. "Proof you can't trust anything in Australian Fairfax papers, unless you are just another crazy," Murdoch tweeted. The News Corp chairman and chief executive's latest Twitter response comes 24 hours after a series of critical tweets apparently responding to the AFR claims and Monday's BBC Panorama documentary alleging that NDS helped computer hackers undermine BSkyB's UK pay-TV rival ITV Digital. Murdoch tweeted that it seemed "every competitor and enemy [is] piling on with lies and libels" and promised that News Corp would "hit back hard". AFR published a series of articles earlier this week making a string of accusations against NDS including that it had a "secret unit" that aimed to undermine News Corp's pay-TV rivals in Australia. Abe Peled, executive chairman of NDS, has written a two-page letter to AFR editor-in-chief Michael Stutchbury demanding an immediate retraction of the allegations. "Despite claiming to have been investigating the issues for four years, it is already apparent that your several recent articles accusing NDS of promoting and facilitating piracy are based on gross mischaracterisations of the evidence," Peled said. The newspaper alleged that NDS set up a security group, called Operational Security, to battle piracy of conditional access cards on behalf of News Corp's Australian pay-TV partners. However, the AFR said a four-year investigation, and access to 14,400 emails from the former European chief of the unit, showed NDS also "encouraged and facilitated piracy by hackers" against rivals. The newspaper reported that its investigation shows a "global trail of corporate dirty tricks", with documents providing evidence that "NDS sabotaged business rivals, fabricated legal actions and obtained telephone records illegally". In the letter Peled said in certain instances the context, and actual text, of emails featured in the AFR story have been "critically misrepresented". He argued that a "shocking manipulation" of the email evidence has twisted a fight against piracy by NDS into stories that it is involved in hacking. "There is no excuse for your repeated failures to tell your readers the truth," said Peled. "The truth is that NDS is a leader in the fight against piracy. And the truth is that NDS has assisted law enforcement agencies around the globe in bringing to justice many of the pirates your articles falsely portray as victims. We demand that you immediately retract your allegations to the contrary." Stutchbury responded: "The Australian Financial Review fully stands by our reports by one of the world's most knowledgeable reporters covering News Corporation. "We are not alleging any illegal activity by News subsidiary NDS but suggest that [reporter Neil] Chenoweth's reports raise serious governance issues ... We have posted thousands of supporting email evidence on our website afr.com.au and welcome any independent investigation of the matter."