An Obama administration official said security personnel thwarted an attempted breach on a White House computer system before the attackers could obtain sensitive data or access classified networks, according to a published report.

"In this instance the attack was identified, the system was isolated, and there is no indication whatsoever that any exfiltration of data took place," the unnamed official was quoted as saying in an article published on Monday by The Hill. "Moreover, there was never any impact or attempted breach of any classified system."

The official said the attack on an unclassified network was carried out through a technique known as spear phishing. It uses e-mail messages that typically address the receiver by name in the hopes of tricking the person into divulging log-in credentials or clicking on a malicious link used to install malware on the end-user computer. Such attacks have become an increasingly common way of targeting government agencies and contractors, as well as Fortune 500 companies.

The White House official spoke after the politically conservative Washington Free Beacon reported on Sunday that spearphishers with ties to China's government "broke into one of the US government's most sensitive computer networks." Reporter Bill Gertz wrote that it was "one of Beijing's most brazen cyber attacks against the United States." The post, which cited unnamed defense and intelligence officials, identified the network as belonging to the White House Military Office (among other things, this entity is in charge of communications involving strategic nuclear commands issued by the US president). Security officials were still working to determine what damage may have been caused, the publication reported.

The dueling reports highlight the difficulty of independently verifying the claims being made by unnamed officials. An official speaking to the Washington Free Beacon said the alleged breach "highlights a failure of the Obama administration to press China on its persistent cyber attacks." Ars readers are advised to remain skeptical of unconfirmed reports involving alleged intrusions on government networks, particularly just prior to a presidential election.