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Stor-a-File hit by ransomware after crooks target SolarWinds Serv-U FTP software

Stor-a-File, a British data capture and storage company, suffered a ransomware attack in August that exploited an unpatched instance of SolarWinds’ Serv-U FTP software.

The company informed its clients about the September attack, and told The Register that it refused to pay. We understand some data has been leaked by ransomware criminals on a Tor blog.

At least one of Stor-a-File’s clients is a medical company, one of whose customers got in touch with El Reg last week.

“The medical company (which I’m not going to name now as they are going through a process of assessing damage, liability, etc.) used Stor-a-file for the scanning of paper documents including medical records,” our reader told us.

In a statement Stor-a-File said: “The incident occurred in September. The ICO and Police were contacted as soon as we knew what had happened. Our clients were informed once it had been established any of their data may have been compromised.”

Reg readers complained to us about the long delay between the ransomware attack and being notified that their data was caught up in it. Some also alleged they had been told the attack took place in August.

“From our investigations,” continued Stor-a-File’s statement, “the incident is limited to the small number of records we hold electronically. Everyone whose data may have been affected has been contacted. The millions of company and organisation records, held physically in boxes on shelves in our warehouses were unaffected.”

We understand that the attack vector was an outdated version of SolarWinds’ Serv-U FTP server software. While we do not know the precise version Stor-a-File was running, in July Microsoft said it had found a critical vulnerability in version 15.2.3 HF1 and earlier builds.

“We have now removed all third party software from our secure system to prevent any similar issues in the future,” said Stor-a-File.

A since-deleted page on Stor-a-File’s website titled “NHS Scanning” was giving 404s when we visited it at the time of writing. A snapshot saved on the Internet Archive shows Stor-a-File provided “document conversion services to the NHS for more than thirty-five years and across more than forty Trusts.” (There were around 200 NHS trusts across the country in 2019.)

We have asked NHS Digital for comment on whether NHS patient data was affected in the breach, though Stor-a-File assured us they were not.

Health records processed by Stor-a-File included HIV and genitourinary clinic records, finance department records and invoices, oncology and HR files “and many more” to quote the firm itself.

Serv-U what now?

Tracked as CVE-2021-35211, the Serv-U vuln allowed an attacker to achieve remote code execution through what Microsoft described as a Return Oriented Programming attack, as we reported at the time.

British infosec firm NCC Group said in an advisory note that it had seen “multiple” instances of the Clop ransomware gang abusing the Serv-U vuln – highlighting that this was not the China-based threat group pointed out by Microsoft as the vuln’s sole exploiter back in July.

“The first indicator of compromise for the exploitation of this vulnerability are suspicious entries in a Serv-U log file named DebugSocketlog.txt. This log file is usually located in the Serv-U installation folder. Looking at this log file it contains exceptions at the time of exploitation of CVE-2021-35211,” said NCC Group. The company also recommended hunting for suspicious PowerShell command execution; full details are available at the link above.

NCC Group added that in October, “three months after SolarWinds released their patch”, it could still find 2,784 vulnerable Serv-U instances accessible from the public internet. Of those, 27 were in the UK – while 1,141 were in China.

The Clop ransomware gang likes targeting FTP software: earlier this year it was behind the dumping online of radar blueprints stolen from Canadian aerospace manufacturer Bombardier. ®