Collusion Detection Software with PT?

[RGL]

Collusion is discussed and/or claimed in these forums from time to time. Support for the claims, however, is almost always anecdotal.

Is there any software program to do analysis on PT data to surface possible collusion?

If not, what approach could be used with PT data to see if such takes place? I'm interested in smaller sites where it is quite common for pairs or groups of players to show up at the same tables on a repeating basis.

Supposedly, sites have programs which look for suspicious behavior. Do you know what there analysis is based on? Or are there good links or previous posts that deal with substantive analysis or an analytical approach?

Thank you for your help.