The Anthem Healthcare breach, which exposed the personal records of 80 million individuals, was the handiwork of Black Vine, a cyberespionage group with the resources to afford its own infrastructure, zero-day vulnerabilities, and custom malware, according to researchers at Symantec.

The group has ties to Topsec, a Beijing-based security research, training, and auditing organization that run an annual hacking competition. Researchers believe Black Vine has been operating from the same region since 2012, aiming cyberespionage campaigns at mostly healthcare and aerospace organizations in the United States.

In addition to Anthem, Symantec is attributing to Black Vine a 2012 attack on gas turbine manufacturer Capstone Turbine, a 2014 attack on a European aerospace company and a 2013 attack against a "global airline." In a separate report by Bloomberg today, unnamed sources "close to the investigations" say that the attackers behind the Anthem breach are also to blame for the breach at the U.S. Office of Personnel Management and had "in recent months" breached United Airlines in a previously undisclosed attack that reportedly exposed travel manifests. United Airlines has not confirmed there is an investigation.

Some of Black Vine's tools and methods are similar to the Hidden Lynx hacker-for-hire APT group based in China. Both use watering-hole attacks -- leaving exploits on websites relevant to targets' interests -- and use the same zero-day vulnerabilities, seemingly obtained via the Elderwood framework, but with different payloads attached.

Black Vine uses custom malware -- Hurix, Sakurel, and Mivast, specifically, which are backdoors for stealing data. Black Vine's custom malware of choice was generally made to look like technology-related applications, with command-and-control server domain names to match, to complete the disguise.

Against Anthem, the group used a variation of Mivast "disguised using Citrix and Juniper VPN lures, indicating that the initial attack may have been aimed at Anthem's technical staff."

However, the Anthem attack was a little different. Although attackers used multiple domains to pose as healthcare and technology-related organizations in the breach, a water-holing attack was never seen or reported, according to the researchers. They say "it is unclear what mechanisms were used to deliver the malware. It is likely that the threat was delivered through spear-phishing."