The Dark Web email service SIGAINT suffered a major attack that involved 70  exit nodes, a circumstance that suggests Government operation.

Law enforcement and Intelligence agencies are always involved in the infiltration of Darknets and related services with the primary intent to monitor bad actors and de-anonymize users.

The Tor-Based Dark Web Email Service SIGAINT is one of the services under constant attack of Government agencies, recently its administrator warned the users of the email service that was targeted by a suspected law enforcement agency who tried to hack it.

SIGAINT is one of the web email service hosted on the TOR network that is used to send messages preserving user’s anonymity.

Among the users of web email services hosted in the dark web, there are journalists, dissidents menaced by repressive regimes and of course intelligence agencies and cyber criminals.

Due to the nature of the service and the identity of its users, SIGAINT email service is one of those Tor hidden services targeted by the intelligence.

According to the Administrator, a persistent attacker with access to nearly 70 bad Tor exit nodes  (around 6 percent of the total) have tried to compromise the email service, the attack occurred a few days ago. The administrator of the anonymous web email service alerted the users via the tor-talk mailing list this week.

Tor Exit Nodes are the gateways where encrypted Tor traffic flows on the Internet, by monitoring an exit node it is possible to analyze the Tor traffic after it leaves the onion network.

In the specific case of web email services like SIGAINT, the Tor exit node is the last hop before the message reaches the Internet and its IP address is the unique information seen by the recipient instead the IP address of the legitimate sender.

One of the administrators of SIGAINT confirmed that his server was targeted by 58 malicious Tor exit nodes, but a member of the Tor Project, Philipp Winter, discovered other 12 bad exit nodes.

A so huge number of exit nodes compromised lead the experts to believe that involvement of an intelligence agency.

“So apparently we have drawn attention to our humble little email service that mostly lives inside of the Tor network. Today we reported 58 bad exit nodes to Philipp. He instantly found 12 more that we had missed, and there may be even more of them. (Thank you, Philipp!) FYI: They were added to the BadExit list just hours ago so traffic to them should dry up. The attacker had been trying various exploits against our infrastructure over the past few months. Our exploit mitigations have been sounding various alarms.” is reported in the tor-talk mailing list.

The managers of the Tor Project have blacklisted the bad Tor relays that were used by attackers to run”man in the middle” (MITM) attacks.

Which is the impact for the victims?

SIGAINT administrators speculate that the service was not compromised, but there is the concrete possibility that attackers have obtained credentials of an unknown number of users.

“We are confident that they didn’t get in,” states the alert. “It looks like they resorted to rewriting the .onion URL located on sigaint.org to one of theirs so they could MITM [man-in-the-middle] logins and spy in real-time.”

The administrator, who wishes to remain anonymous, told Motherboard that the hackers failed to break into SIGAINT’s servers.

“We know what they were after,” the admin told to Lorenzo Bicchierai at Motherboard. “There is no way to spy on email that doesn’t leave the darknet without spying on the mail service itself.”

The SIGAINT email web service is evaluating the possibility to enable encryption by default or remove the .onion URL from the sigaint.org page.

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Pierluigi Paganini

(Security Affairs –  SIGAINT, Deep Web)