KIEV (Reuters) – The government of Ukraine, which was victim of a major cyber attack earlier this year, told businesses on Friday to make sure their networks were protected because of intelligence suggesting that another attack may be in the works.

Ukraine’s state security service SBU and the state-run Computer Emergency Response Team (CERT) said the attack could take place Oct. 13-17 when Ukraine celebrates Defender of Ukraine Day.

Ukraine, which believes Russia is behind regular attacks on its computer systems, is trying to roll out a national strategy to keep state institutions and major companies safe. Moscow denies that it is behind cyber attacks on its neighbor.

The security agencies said that a new attack may be similar to the NotPetya computer virus which struck on June 27 taking down computers in Ukrainian government agencies and businesses before spreading rapidly through corporate networks of multinationals with operations or suppliers in eastern Europe.

(Reporting by Pavel Polityuk; editing by Peter Graff)