The Pentagon says that a Joint Chiefs of Staff computer network taken offline last week after it was discovered to have been infiltrated by hackers is once again up and running.
A spokeswoman for the Department of Defense said on Monday that the Pentagon’s cybersecurity team had purged the infected network of malware, locked out any unauthorized individuals who may have gained access and implemented new protective measures intended to prevent further break-ins.
“While any intrusion or attack upon our network is troubling, each attempt to intrude upon our networks offers a learning opportunity to improve our ability to effectively respond and bolster our cyber defenses and network security,” Defense Department spokeswoman Lt. Col. Valerie Henderson said in a statement, The Hill reported. “We have full confidence in the integrity of the DOD networks and systems.”
The network, which ran an unclassified email system used by the Joint Chiefs, was found late last month to have been compromised by hackers. Some U.S. officials have blamed Russian actors with the cyberattack, but they have yet not officially confirmed the attribution.
Around 4,000 workers with the Joint Chiefs lost access to their email accounts while the Pentagon spent several weeks investigating the breach and wiping the network clean.
“Given indicators of suspicious activity, elements of our cyber workforce isolated the Joint Staff unclassified network from the larger DOD information network and the Internet,” Col. Henderson said.
“Isolating the Joint Staff network enabled us to conduct a systematic process to hunt for adversaries, mitigate any malicious activity, confirm network security and integrity and further harden defenses.”
She said the hackers conducted a “broad phishing campaign” in which targeted account holders were tricked into clicking on malicious links sent via email. FireEye, a leading U.S. security company, reported previously that targeted phishing operations, or “spear phishing” campaigns, are successful roughly 70 percent of the time.
Defense officials said no classified information was compromised in the attack, NBC News reported.
Earlier on Monday, however, the network published a separate report in which it was revealed through leaked national security documents that the U.S. intelligence community believes cyberspies acting on behalf of China had set their sights on “all top national security and trade officials” in the White House and had managed to compromise “many” of their personal email accounts.
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