Exposed services · VNC

Is it safe to leave VNC screen sharing reachable from the internet?

No.

Last read from the sources at the foot of this page.

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01

What is VNC?

Virtual Network Computing (VNC) shares a computer's screen, keyboard and mouse with someone elsewhere. It usually listens on port 5900.

It is often installed for a one-off support session and then left running.

02

Why does it matter?

Remote Shell (RSH), Secure Shell (SSH), Server Message Block (SMB), Virtual Network Computing (VNC), and X11 (X Window System).

CISA's directive on internet-exposed management interfaces, issued 13 June 2023, names Virtual Network Computing (VNC) among the protocols it covers.

Whoever gets past a VNC password sees and controls the screen as if they sat at the desk.

03

What do I do about it?

  1. Remove any port forwarding rule for 5900 in your router or firewall.
  2. Uninstall VNC from computers that no longer need it.
  3. Where it is needed, reach it only through a VPN with multi-factor sign-in.
  4. Set a strong VNC password and keep the software updated.
Sources

Where does this come from?

Related
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