A software \"worm\" evidently unleashed by hackers burrowed through Tumblr on Monday, defacing pages at the popular blogging platform with a vitriolic, expletive-laden message. A hacker group going by the acronym \"GNAA\" claimed responsibility for the diatribe, which dismissed most of what bloggers shared online as worthless. \"Tumblr engineers have resolved the issue of the viral post attack that affected a few thousand Tumblr blogs earlier today,\" the US-based company said in an email response to an AFP inquiry Monday. Tumblr reports that it is home to 83.2 million blogs that jointly attract about 18.2 billion page views monthly. High-profile Tumblr blogs defaced by the worm were said to include those of CNET and The Verge.