Jan's last diary about the recent attack against the US pipeline[1] was in perfect timing with the quick research I was preparing for a few weeks. If core components of industrial systems are less exposed in the wild, as said Jan, there is another issue with such infrastructures: remote access tools. Today, buildings, factories, farms must be controlled remotely or sometimes managed by third parties. If Microsoft RDP is common on many networks (and is often the weakest link in a classic attack like ransomware), there is another protocol that is heavily used to remote control industrial systems: VNC ("Virtual Network Computing")[2]. This protocol works with many different operating systems (clients and servers), is simple and efficient. For many companies developing industrial systems, It is a good candidate to offer remote access. 

To give you an idea of the VNC popularity on the Internet, Shodan report this number of available systems:

• Port 5900: 907.387 hosts
• Port 5901: 738.545 hosts

Note: VNC uses by default the port 5900+n, where n is the display number (usually :0 for a physical display).

I had a look at open port 5900 & 5901 and captured 655K exposed VNC servers. Don't take me wrong, I don't say that VNC is bad. I still use it almost weekly but, like all tools, it must be configured and used in a proper way. Read: access must be restricted (passwords, access-lists) and traffic encrypted. My next step was to hunt for open VNC console (without any authentication). I did not brute force passwords or tried even simple passwords like "admin". I used the tool vncsnapshot[3] to take screenshots of non-protected systems through the Tor Network. 

Based on the sample screenshots below, you realize that many organizations are at risk, and many bad stories like the US pipeline attack will continue to raise in the news...

[1] https://isc.sans.edu/forums/diary/Number+of+industrial+control+systems+on+the+internet+is+lower+then+in+2020but+still+far+from+zero/27412/
[2] https://en.wikipedia.org/wiki/Virtual_Network_Computing
[3] https://github.com/IDNT/vncsnapshot

Xavier Mertens (@xme)
Senior ISC Handler - Freelance Cyber Security Consultant
PGP Key