Hackers have broken into the computer network of the Polish president's office and attempted to spread a computer virus in the form of an email attachment.
Similar incidents have taken place at several other government offices this month, including the Defence and Foreign Affairs Ministries.
CERT Polska, a computer emergency response team in Poland that is run under the aegis of the country's Research and Academic Network (NASK), has announced takedown action against a raft of web servers associated with the Virut family of malware.
Most zombies rely on connecting to so-called C&C (command-and-control) servers to find out what to do next.
Several Polish government websites, including that of the parliament and the prime minister, appear to have been disrupted over the weekend by online activists.
The attacks began late Saturday and lasted through Sunday morning,.
The affected websites were inaccessible or extremely slow.
An informal group of hackers who said were linked to the international hacking organization Anonymous took credit for the online attack meant as protest against the government's plans to sign the treaty, known as ACTA, they said in statement put on YouTube video-sharing website.
Politicians associated with the opposition Law and Justice (PiS) party are included on a list of “Polish neo-nazis” uploaded onto the internet by the Anonymous hacking group.
The data is part a trove of information, including emails, passwords and credit card details hacked by the Anonymous collective over the past few weeks, including data taken from the US-based Stratfor security analyst company over the Christmas period.
