The US Department of Homeland Security has said that a series of distributed denial-of-service attacks began on US government networks on 4 July.
However, Amy Kudwa, deputy press secretary for the US DHS, told ZDNet UK on Wednesday that attacks on federal systems were common, and that the US Computer Emergency Response Team could deal with them.
"We see attacks on federal networks every day, and measures in place have minimized the impact to federal websites," said Kudwa. "US-CERT will continue to work with its federal partners and the private sector to address this activity."
Kudwa declined to say which websites had been attacked, but said that both public and private sector websites had been affected.
"DHS is aware of distributed denial-of-service attacks on federal and private sector public-facing websites," said Kudwa. "The department's US-CERT has issued a notice to federal departments and agencies, as well as other partner organizations, on this activity and advised them of steps to take to help mitigate against such attacks."
The BBC reported that the White House, Defense Department and New York stock exchange were all targeted.
The Treasury Department, a part of the Secret Service site, the Federal Trade Commission, and the Transportation Department had also been under attack, a US government source told ZDNet UK. While there was some slight slowing of US government networks, on the whole the attacks had not had much effect, said the source.
Reports that the attacks may be coming from North Korea could be premature, the government source added, saying that DDoS attacks are often difficult to attribute.