WASHINGTON (AP) — After the U.S. government disclosed its first technical report publicly connecting Russia's intelligence services to U.S. hacking, the phones started ringing inside cybersecurity firm Rendition Infosec LLC.

Worried customers were following the government's advice, issued Dec. 29, and comparing digital logs recording incoming network traffic to their computers and finding matches to a list of hundreds of internet addresses the Homeland Security Department had identified as indicators of malicious Russian intelligence services cyber activity.

"They thought they were compromised," said Rendition founder, Jake Williams, who described a "frenzy" of computer security specialists scrubbing their systems for signs of the Russians. The firm sent a cautionary note to businesses telling them, "be very, very careful on applying this," and encouraging them to look for further evidence before raising alarms.

The incident illustrated the difficulties and dangers of imprecise government warnings on cybersecurity, especially when national security concerns are at play and sensitive details may compromise information sources. Alerts that are too vague aren't meaningful. Alerts with details but lacking context might generate false positives, unnecessarily costing businesses and spreading panic among internet users — or worse, damaging the credibility of the government about its future warnings.

A Homeland Security Department official, speaking on condition of anonymity, defended the recent warnings. The official acknowledged the listed addresses included legitimate activity but said businesses were advised to investigate further traffic from those addresses because the Russians are sophisticated adversaries who hide their activities among ordinary internet traffic.

Robert M. Lee, CEO of the Maryland-based industrial security firm Dragos Inc., warned his customers, who span critical infrastructure including water, electric, manufacturing and petro-chemical sites, that the technical information was bad. About one dozen called with concerns.

"Every single company we have as a customer who ran the indicators got alerts, and all the alerts were bad," Lee said. "These addresses were not only not descriptive of Russian activity, they were not descriptive of malicious activity. They were actually common sites."

The Associated Press found that nearly one quarter of the internet addresses identified by the Obama administration as potentially tied to Russian activity had traced back to computer servers that help users browse the internet anonymously. That service, called Tor, was initially funded by the U.S. government and is now used prominently by activists and journalists working in hostile countries who need to keep their identities a secret.

Other internet addresses released by the Homeland Security Department traced to servers at American universities and email provider Yahoo Inc. The government cautioned that the addresses weren't automatically tied to Russian malicious activity, but instead were indicators that computer security experts should investigate further.

One of the businesses that called Williams reported that an address tracked to Microsoft's telemetry server, which sends data to Microsoft when an application crashes. That conversation with his client spun into an hour-long discussion of "can we trust this report at all?" Williams said. "My short answer on this is no."

He added: "This has a real cost to business. I suspect for a lot of them there (was) a lot of money spent chasing ghosts."

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