After Symantec blew the lid on Regin on Sunday, computer security experts and companies are revealing information that has lead to suspicions that the US and UK are involved.
Regin has been known about for years by security companies, but Symantec's white paper on the malware prompted several in the last day to come forward with what they know.
It's unclear why security companies maintained a collective silence about Regin for so long. Symantec said it first discovered Regin about a year ago and that it took the company that long to analyze it.
Within a day of Symantec's report, rival Kaspersky Lab had published a 28-page whitepaper of its own, indicating that the company was well-prepared for when Regin became public.
The Regin platform is considered highly sophisticated due to its use of encryption and modular components, which made it hard for analysts to figure out.
It was used against telecom companies, ISPs, small businesses and individuals, with the aim of collecting login credentials and sensitive data, including infiltrating GSM base stations. Symantec said many of the targets were in Russia and Saudi Arabia.
The Intercept reported on Monday that it was Regin which struck the telecommunications company Belgacom and was used against European Union targets. The publication said its conclusion is based on a technical analysis of the malware and sources who investigated those attacks.
Documents leaked by former U.S. National Security Agency contractor Edward Snowden indicated that Belgacom was targeted by the British intelligence agency Government Communications Headquarters (GCHQ) as part of Operation Socialist, according to Der Spiegel.
The Snowden documents revealed many methods of attack and targets of the NSA and GCHQ, which have conducted sophisticated and extensive data collection operations.
NSA spokeswoman Vanee M. Vines wrote via email Monday that the agency would not comment on The Intercept's "speculation."
Kaspersky Lab wrote on Monday it obtained a sample of malware that had infected the computer of Jean Jacques Quisquater, a well-known Belgian cryptographer who said his computer was targeted by a sophisticated attack.
Quisquater told IDG News Service in February that investigators from the Belgian Federal Computer Crime Unit (FCCU) told him that the attack against his laptop was directly related to the Belgacom incident.
"We were able to obtain samples from the Quisquater case and confirm they belong to the Regin platform," according to Kaspersky's white paper.
Ronald Prins of Fox-IT, a computer forensics company, told The Intercept his company investigated the attacks against Belgacom. Prins told the publication that Regin was the most sophisticated malware he has ever studied and that he was "convinced" it was used by U.S. and U.K. intelligence services.
Other computer security companies have been less direct about Regin's creator. Symantec maintained that it believed Regin was of such clever engineering that it must have been developed by a nation-state, but it stopped short of naming one.
In a statement on Monday, Symantec said it has not found any identifiers in Regin's code that indicate its origin and that "we do not have sufficient evidence to attribute it to any particular state or agency."
The Finnish computer security company F-Secure saw an early version of Regin in 2009 and also shied away from naming a country.
But Antti Tikkanen, director of security response at F-Secure Labs, wrote in a blog post: "Our belief is that this malware, for a change, isn't coming from Russia or China."
F-Secure found Regin on a server run by one of its customers in northern Europe. The server was occasionally crashing and showing the Blue Screen of Death, Tikkanen wrote. The cause was a driver that turned out to be a rootkit and an early Regin variant.
Mikko Hypponen, F-Secure's chief research officer, wrote on Twitter that F-Secure added detection for Regin, but didn't write about it publicly due to customer confidentiality concerns.
Hypponen maintained that F-Secure added detection for Regin in its products and that "no customer (and no government) has ever asked us not to add detection on some specific malware."
Microsoft also picked up on Regin, adding an entry for a variant into its database of malware on March 9, 2011. The entry, however, contains no technical data.
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