> how to find out if there is anyone running wireshark on my network?
I think you have to ask all users on your network whether they run it.
I assume you ask motivated by the situation someone could use it
unauthorizedly, such as from a hacked host?
You cannot detect passive eavesdropping (unless using quantum
cryptography :)) from the network (you could only use SSH and check each
machine, but if it is hacked the root kit will hide all sniffing tools
anyway, so even this won't help...
oki,
Steffen