SIP irule for checking dialed string

Thanks Syed, It's a bit more complicated because we may have valid SIP request without any meeting number: like sip: or sip:.

Here is the final version of my irule:

when SIP_REQUEST {
    if { [SIP::method] == "INVITE" && [SIP::uri] matches_regex {^.+@.+$} }
    {
        if { not ([SIP::uri] matches_regex {^(sip:|sips:)[0-9]{7}@}) }
        {            
            log local0. "SIP Drop for [SIP::uri] from [IP::remote_addr] - possible frauder"
            drop   
        }

    }
}

I hope this can be useful for other people having similar case.

regards, Evelin