Breach at Deloitte Exposes Emails, Client Data

Big Four accounting giant and cybersecurity consultancy Deloitte has suffered a data breach that ironically enough may have resulted from the firm's failure to follow its own security advice to clients.

The Guardian on Monday reported that an intrusion at Deloitte between October and November last year exposed emails containing highly sensitive data belonging to an unknown number of large US companies and government organizations.

The intrusion, which Deloitte did not discover until March 2017, apparently stemmed from the company's failure to use two-factor authentication to protect a critical administrator account — something that it advocates as a best practice for clients. Attackers used the account to get privileged and unrestricted access to Deloitte's entire Azure-hosted email system.

During the multiple months that the threat actors managed to remain undetected on Deloitte's network, they potentially had access to some 5 million emails. The attackers also had potential access to usernames, passwords, health information, and highly sensitive data belonging to an unspecified number of Deloitte's clients, The Guardian said.

Deloitte itself has claimed that the actual number of emails and the scope of the data that was affected is only a "fraction" of the number suggested by The Guardian.

In an emailed statement to Dark Reading, Deloitte confirmed the breach and said the attackers had accessed data from the company's email platform. Deloitte's investigation of the incident has enabled it to understand precisely what data was at risk and what the attackers actually accessed.

Only a "very few" clients were affected, the company said. "No disruption has occurred to client businesses, to Deloitte's ability to continue to service clients, or to consumers," the statement noted. Deloitte immediately informed the appropriate government authorities upon breach discovery and contacted each of the clients that were affected, it added.

It's unclear how the threat actor might have obtained access to the administrator account that The Guardian reported as being used for the theft. But the company's apparent failure to properly protect it came in for some criticism Monday from security executives. 

Several feel that the company, as one of the largest cybersecurity consultancies in the industry, should have known better than to use a single password for the account, especially at a time when credential theft and misuse have become rampant.

"Clearly, they don't exactly practice what they preach," says Gaurav Banga, founder and CEO of Balbix. Based on the details available so far, the attack itself does not appear to be particularly sophisticated, he says. "If there is no two-factor authentication on administrative accounts, and unencrypted emails are floating around, then the adversary does not need to work very hard after an initial breach-head is established."

The apparent fact that Deloitte did not discover the intrusion for several months is not entirely surprising in this context, adds Rich Campagna, CEO of Bitglass.

"Breaches involving credential compromise often take months to identify and remediate," he says. "From an IT perspective, it can be difficult to notice unusual activity from hijacked accounts — it may simply appear that users are going about their jobs normally. At Deloitte's scale, manual review of each somewhat suspicious transaction isn't a feasible option."

The main takeaway from incidents like these is that organizations must mandate two-factor authentication on all external accounts and services, adds Mark Dufresne, director of threat research and adversary prevention at Endgame.

"This is another example of a case in which the actors didn't need exploits or malware to gain access," says Dufresne, "but were simply able to capitalize on employees' poor cyber hygiene."

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