The massive hacking campaign disclosed by U.S. officials this week and tentatively attributed to the Russian government extended beyond users of pervasive network software that had been compromised.
The Department of Homeland Security said in a bulletin on Thursday that the spies had used other techniques besides corrupting updates of network management software by SolarWinds , which is used by hundreds of thousands of companies and government agencies.
“The SolarWinds Orion supply chain compromise is not the only initial infection vector this APT actor leveraged,” said DHS’s Cybersecurity and Infrastructure Security Agency (CISA), referring to “advanced persistent threat” adversaries.
CISA urged investigators not to assume their organizations were safe if they did not use recent versions of the software, while also pointing out that the hackers did not exploit every network they did gain access to.
CISA said it was continuing to investigate the other avenues used by the attackers. So far, the hackers are known to have at least monitored email or other data within the U.S. departments of defence, state, treasury, homeland security and commerce.
As many as 18,000 Orion customers downloaded the updates that contained a back door that let hackers in. Since the campaign was discovered, software companies have cut off communication from those back doors to the computers maintained by the hackers.
But the attackers might have installed additional ways of maintaining access in what some have called the biggest hack in a decade.
For that reason, officials said that security teams should communicate through special channels to ensure that their own detection and remediation efforts are not being monitored.
The Department of Justice, FBI and Defence Department, among others, have moved routine communication onto classified networks that are believed not to have been breached, according to a person briefed on the measures.
CISA and private companies including FireEye, which was the first to discover and reveal it had been hacked, have released a series of clues for organizations to look for to see if they have been hit.
On Thursday afternoon, Microsoft said it detected a malicious version of software from SolarWinds inside the company but that its investigation so far showed no evidence hackers had used Microsoft systems to attack customers.
“We detected malicious SolarWinds binaries in our environment, which we isolated and removed,” a Microsoft spokesperson said, adding that the company had found “no indications that our systems were used to attack others.”
However the attackers have been very careful and have deleted logs of which files they have accessed. That makes it hard to know what has been taken.
One person familiar with the hacking spree said the hackers made use of Microsoft cloud offerings while avoiding Microsoft’s corporate infrastructure.
Microsoft did not immediately respond to questions about the technique.
Still, a person familiar with the matter said the Department of Homeland Security does not believe Microsoft was a key avenue of fresh infection.
In most networks, the attackers would also have been able to create false data, but so far it appears they were interested only in obtaining real data, people tracking the probes said.
Meanwhile, members of Congress are demanding more information about what may have been taken and how, along with who was behind it. The House homeland security committee and oversight committee announced an investigation Thursday, while senators pressed to learn whether individual tax information was obtained.
The FBI and other agencies have scheduled a classified briefing for members of Congress on Friday.
In a statement, president-elect Joe Biden said he would “elevate cybersecurity as an imperative across the government” and “disrupt and deter our adversaries” from undertaking such major hacks.