NSA warns Russian hackers exploited email flaw

Russian hackers have compromised a longstanding vulnerability in a widely used email delivery software program since at least August of last year, according to an advisory from the National Security Agency.

The flaw is serious, and allows what NSA characterizes as "pretty much any attacker’s dream access." It allows hackers to turn off network security, add privileged users and enable remote connections and subsequent penetrations.

A Russian military intelligence team called Sandworm is responsible, NSA says, for leveraging a flaw in the Exim Mail Transfer Agent software – a program in very wide use by email administrators. An estimate from last October indicated that Exim was in use in almost 500,000 email servers worldwide, and was by far the most widely used software of its type. NSA notes that Exim is the default software on some Linux-based email systems.

The vulnerability was introduced in a June 2019 update, NSA says, and was remediated in the most recent version of the software. Exim has been publicly urging users to update even before NSA revealed the exploitation of the flaw. NSA is urging administrators to conduct checks for prior exploitation on their networks and by looking for unauthorized accounts or remote access authorizations.

Sandworm, an element of Russia's GRU, has been blamed for the devastating NotPetya cyberattack that crippled the systems of global shipping firm Maersk and cost global firms upward of $1 billion in mitigation and recovery costs. Sandworm has also been linked to efforts to compromise the mobile operating system Android and attempts to target the U.S. electrical grid.

The group was also called out in a Feb. 20 statement by the Department of State for a cyberattack that disrupted government websites and broadcast television in the Republic of Georgia.

"This action contradicts Russia's attempts to claim it is a responsible actor in cyberspace and demonstrates a continuing pattern of reckless Russian GRU cyber operations against a number of countries," Secretary of State Mike Pompeo said at the time.