According to certain officials of the United States, hackers from Russia that carried out the damaging hack against the State Department over recent months used the successful infiltration to gain entry into sensitive components of the computer system of the White House.

The White House previously reported that the security breach only affected unclassified portions of its networks, with no signs that the classified parts have likewise been breached. Intelligence officials then already believed that the attackers were from Russia.

However, despite only gaining entry into the unclassified parts of the White House's system, the situation is still considered very serious. Through their security breach, the hackers were able to access sensitive information including real-time but private details of the schedule of the president. Such information, while not classified, is still very sensitive and highly valued by foreign intelligence groups.

Suspicious activity was reported in October of last year within the unclassified portions of the network of the White House, leading to periodic shutdowns for upgrades to network security.

The hacking, which is being investigated by U.S. intelligence agencies with the Secret Service and the FBI, is being considered as one of the most sophisticated cyberattacks ever carried out against the United States government. The security breach travelled through computers located all over the world, as hackers often do to make it difficult to trace the attack back to them, but investigators have found signs that point to the high possibility that the hackers are working for the government of Russia.

When contacted for comment by CNN, the Russian Embassy and the U.S. State Department did not immediately respond. Mark Stroh, a spokesman for the National Security Council, also did not confirm that the hack was launched by Russia.

Ben Rhodes, the deputy national security adviser to President Barack Obama, reiterated in an interview with Wolf Blitzer of CNN that there are no signs that the classified parts of the White House's networks have been compromised.

Rhodes added that there are ongoing constant updates to the security measures of the unclassified parts of the White House's networks.

Investigators think that the hackers first breached the State Department, which shows signs that despite additional security measures to drive out the attackers, the hackers are still able to regain access to the State Department's systems. An official even said that the hackers have "owned" the system of the State Department for several months.

Investigators also believe that the hackers were able to then gain entry into the White House networks through a phishing email to one of its employees sent by a compromised email account from the State Department.

Photos: Tom Lohdan and Ivan David Gomez Arce | Flickr