The user agent whitelist/blacklist is based on the User-Agent header in the SIP INVITE. To whitelist/blacklist by user agent, the appropriate header must be present in the SIP INVITE to communicate the information to ClearIP. ClearIP does not recognize user agent information presented in the SDP.
User-Agent Header
Here is an example SIP Invite with a User-Agent header.
INVITE sip:900447418600363@1.1.1.1:5060 SIP/2.0
Via: SIP/2.0/TLS 1.1.1.1:5061;branch=z9hG4bKe7e8.0a760738569ce2a5740acf005cc50ee1.0
Via: SIP/2.0/UDP 2.2.2.2:33237;received=2.2.2.2;branch=z9hG4bKd7b61754-peVuTzJrb8eYDOAO;rport=11648
Contact: <sip:53126391@2.2.2.2:33237>
From: <sip:53126391@2.2.2.2:33237>;tag=nRYkObYJXWwH
To: <sip:900447418600363@1.1.1.1:5060>
Call-ID: FAF0TRTW54ZH.3126391.N141CAHS0H5W
CSeq: 1 INVITE
User-Agent: PortSIP VoIP SDK 11.2
Max-Forwards: 69
Allow: ACK,CANCEL,INVITE,MESSAGE,BYE,OPTIONS,INFO,NOTIFY,REFER
Content-Type: application/sdp
Content-Length: 441
v=0
o=CiscoSystemsSIP-GW-UserAgent 1468393932 1468397615 IN IP4 2.2.2.2
s=SIP Call
c=IN IP4 2.2.2.2
t=0 0
m=audio 20002 RTP/AVP 9 104 98 3 8 0 18 101
a=rtpmap:9 G722/8000
a=fmtp:9 bitrate=64000
a=rtpmap:104 G726-16/8000
a=rtpmap:98 iLBC/8000
a=fmtp:98 mode=20
a=rtpmap:3 GSM/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=sendrecv
If the SIP Invite contains a User-Agent header, then in the SIP Messages page, then the user agent name is populated in the User Agent column. 
Blacklist Specific User Agent
ClearIP can be used to blacklist a specific user agent. 