Facebook Google Plus Twitter LinkedIn YouTube RSS Menu Search Resource - BlogResource - WebinarResource - ReportResource - Eventicons_066 icons_067icons_068icons_069icons_070

Tenable Blog

Subscribe

Active and Passive TOR Detection

Tenable's research group has recently released several updated plugins for both the Nessus scanner and Passive Vulnerability Scanner to detect Tor in operation and waiting for connections.

Tor is a self organizing peer-to-peer network application. It encrypts network communications and also randomly spreads it across other Tor nodes to prevent traffic analysis.

Tor can be used for anonymous network browsing. It has recently been reported as being used by the Storm worm to connect to other potential victims as well as obtain command and control instructions.

Hostile "Tor users" have been running a Tor network "end node" in order to monitor and sniff unencrypted exit traffic for sensitive information.

Detecting Tor

Nessus plugin #26026 (currently available to Direct Feed customers) can be used to scan a network for systems configured as a Tor server.

For the Passive Vulnerability Scanner, several plugins exist

  • 2542 - Tor Tunnel Detection (detects on start of Tor communication)
  • 2543 - Tor Tunnel Detection (detect ongoing Tor communication)
  • 4212 - Tor Tunnel 'End Point' Server Detection

When analyzing a network that contains Tor applications, you should ask yourself the following questions:

  • Does carrying this anonymous traffic expose my network to risk?
  • Does the presence of Tor indicate that the network has been compromised?
  • Has there been an increase in the amount of virus, IDS or other types of alerts from the systems running the Tor software?
  • Does the host running Tor consume noticeable network bandwidth?
  • Does Tor open up any unauthorized or un-auditable connections into our network?

Below is a screen shot of a node discovered to be running Tor as viewed under the Security Center. This particular host also has a version of Firefox which is fairly outdated.

Torvulns

This site also was running the Log Correlation Engine with a Tenable Network Monitor. When viewing the last 25 days of network connections from this node, several were made to ports in the 9000-9100 range which is common for Tor communication. Below is a bar chart port summary of all TCP and UDP network connections.

Torports

This discovered Tor node was a client. If it were a Tor end server, the Log Correlation Engine and Tenable Network Monitor agent could have been used to analyze all "outbound" network connections.

For More Information

Nessus active network scans do not discover clients with installed Tor software. Tor clients don't have open ports which can be identified with traditional network connection requests and fingerprints.

If this is a requirement, consider performing a credentialed network scan and enumerate the installed software. Keep in mind that if you want to find out this sort of information in real time, you should use a network IDS or monitor the network with the Passive Vulnerability Scanner.

For other thoughts on passive network monitoring, we've blogged before about several different methods such as watching for new ports being browsed on, detecting network proxies and monitoring traffic for known and unknown encryption.

Related Articles

Cybersecurity News You Can Use

Enter your email and never miss timely alerts and security guidance from the experts at Tenable.

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy.

Your Tenable Vulnerability Management trial also includes Tenable Lumin and Tenable Web App Scanning.

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

100 assets

Choose Your Subscription Option:

Buy Now

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy.

Your Tenable Vulnerability Management trial also includes Tenable Lumin and Tenable Web App Scanning.

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

100 assets

Choose Your Subscription Option:

Buy Now

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy.

Your Tenable Vulnerability Management trial also includes Tenable Lumin and Tenable Web App Scanning.

Tenable Vulnerability Management

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

100 assets

Choose Your Subscription Option:

Buy Now

Try Tenable Web App Scanning

Enjoy full access to our latest web application scanning offering designed for modern applications as part of the Tenable One Exposure Management platform. Safely scan your entire online portfolio for vulnerabilities with a high degree of accuracy without heavy manual effort or disruption to critical web applications. Sign up now.

Your Tenable Web App Scanning trial also includes Tenable Vulnerability Management and Tenable Lumin.

Buy Tenable Web App Scanning

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

5 FQDNs

$3,578

Buy Now

Try Tenable Lumin

Visualize and explore your exposure management, track risk reduction over time and benchmark against your peers with Tenable Lumin.

Your Tenable Lumin trial also includes Tenable Vulnerability Management and Tenable Web App Scanning.

Buy Tenable Lumin

Contact a Sales Representative to see how Tenable Lumin can help you gain insight across your entire organization and manage cyber risk.

Try Tenable Nessus Professional Free

FREE FOR 7 DAYS

Tenable Nessus is the most comprehensive vulnerability scanner on the market today.

NEW - Tenable Nessus Expert
Now Available

Nessus Expert adds even more features, including external attack surface scanning, and the ability to add domains and scan cloud infrastructure. Click here to Try Nessus Expert.

Fill out the form below to continue with a Nessus Pro Trial.

Buy Tenable Nessus Professional

Tenable Nessus is the most comprehensive vulnerability scanner on the market today. Tenable Nessus Professional will help automate the vulnerability scanning process, save time in your compliance cycles and allow you to engage your IT team.

Buy a multi-year license and save. Add Advanced Support for access to phone, community and chat support 24 hours a day, 365 days a year.

Select Your License

Buy a multi-year license and save.

Add Support and Training

Try Tenable Nessus Expert Free

FREE FOR 7 DAYS

Built for the modern attack surface, Nessus Expert enables you to see more and protect your organization from vulnerabilities from IT to the cloud.

Already have Tenable Nessus Professional?
Upgrade to Nessus Expert free for 7 days.

Buy Tenable Nessus Expert

Built for the modern attack surface, Nessus Expert enables you to see more and protect your organization from vulnerabilities from IT to the cloud.

Select Your License

Buy a multi-year license and save more.

Add Support and Training