"CENTCOM's operational military networks were not compromised and there was no operational impact to US Central Command," the statement, released Monday, says.
According to the statement, an "initial assessment" indicated that "no classified information was posted and that none of the information posted came from CENTCOM's server or social media sites".
According to the statement, these sites reside on commercial, non-Defense Department servers.
"Both sites have been temporarily taken offline while we look into the incident further," CENTCOM said in the Monday statement, adding that service to the sites will be restored as quickly as possible.
CENTCOM stressed that it is considering the cyber-attack "purely as a case of cybervandalism" and that all appropriate steps are being taken to ensure any individuals potentially affected are notified as quickly as possible.
Simultaneously, a nearly three minute YouTube video in Arabic with flashing English wording was posted on Central Command's account before being removed. The flashy video showed fighters and tanks and praised the virtues of the IS extremist group, calling for revenge.
CENTCOM is currently running the US-led international campaign against IS militants in Iraq and Syria. The command regularly posts updates on Twitter of airstrikes against IS targets conducted in the two countries.