FBI Director James Comey at a meeting with US Attorney General Jeff Sessions at the Justice Department in Washington. Thomson Reuters The FBI is examining why a computer server for a Russian bank led by oligarchs with close ties to Russian President Vladimir Putin had a disproportionate interest in reaching a server used by the Trump Organization during the US presidential campaign.

CNN reported on Thursday that last summer a computer server owned by the Russia-based Alfa Bank "repeatedly looked up the contact information for a computer server being used by the Trump Organization — far more than other companies did, representing 80% of all lookups to the Trump server."

Slate and The New York Times first reported on the unusual server activity, which was akin to looking up someone's phone number thousands of times.

The Times reported on October 31 that the FBI examined the server activity and "ultimately concluded that there could be an innocuous explanation, like a marketing email or spam, for the computer contacts."

The Intercept reported later that the computer analysts who had first noticed the unusual server activity did not respond to questions about "how they can be sure that the majority of DNS look-ups for Trump's email server originated from Alfa Bank, when much of the data they collected didn't even include DNS look-ups from IPs described in their own paper."

"The simplest plausible explanation for all of this: The Trump Organization owns a bunch of expensive, obnoxious spam servers that churn out marketing emails for its expensive, obnoxious hotels," The Intercept said.

But CNN's reporting indicates that the FBI has not dropped the subject and is still examining the activity as part of its counterintelligence investigation into Russia's interference in the US election.

"One US official said investigators find the server relationship 'odd' and are not ignoring it," CNN reported. "But the official said there is still more work for the FBI to do. Investigators have not yet determined whether a connection would be significant."

Heat Street reported last November that the FBI had sought and obtained a warrant from the Foreign Intelligence Surveillance Court after presenting evidence "of a server, possibly related to the Trump campaign, and its alleged links to two banks; SVB Bank and Russia's Alfa Bank."

Two months later, the BBC reported that the FBI — part of a counterintelligence task force led by the CIA — requested the FISC warrant to investigate the banks after former CIA Director John Brennan received a recording of a conversation about Kremlin money potentially going into Trump campaign coffers.

McClatchy then followed up less than week later, reporting that investigators were "examining how money may have moved from the Kremlin to covertly help Trump win." McClatchy didn't mention Alfa Bank or computer servers and couldn't independently confirm the existence of a FISC warrant.

But a source confirmed to McClatchy that investigators had been given permission to access "bank records and other documents about potential payments and money transfers related to Russia."

CNN's FBI source said there was no FISC warrant on the server, but the FBI declined to comment when asked whether a FISC warrant had been granted at all to look into contact between Russian banks and the Trump campaign that may not have been confined to a computer server.

Alfa Bank was discussed at length in an explosive but unverified dossier detailing the Trump campaign's ties to Russia — though it was misspelled as "Alpha" throughout — raising further questions about the bank's apparent involvement in the unusual server activity.

"Speaking to a trusted compatriot in mid-September 2016, a top level Russian government official commented on the history and current state of relations between President Putin and the Alpha Group of businesses led by oligarchs Mikhail Fridman, Petr Aven and German Khan," the dossier said.

Fridman is the founder of Alfa Bank, Petr Aven was the bank's president from 1994 to 2011, and German Khan is on the bank's supervisory board.

"The Russian government figure reported that although they had had their ups and downs, the leading figures in Alpha currently were on very good terms with Putin," the dossier said. "Significant favors continued to be done in both directions, primarily political ones for Putin and business/legal ones for Alpha."

Fortune reported in November that the oligarchs who controlled Alfa Bank, while politically powerful, were also "the most enduringly successful, western-oriented (if hard-edged) capitalists in Russia," and were therefore unlikely to feel loyal to Putin.

The dossier acknowledged that, writing that the Putin-Alfa relationship was "both carrot and stick."