TSRef - TypoScript Reference
4.1.14. usergroup
Syntax:
[usergroup = group1-uid, group2-uid, ...]
Comparison:
The comparison can only return true if the grouplist is not empty (global var "gr_list").
The values must either exists in the grouplist OR the value must be a "*".
Example:
This matches all logins
[usergroup = *]
This matches logins from users members of groups with uid's 1 and/or 2:
[usergroup = 1,2]