Jason Haar wrote:
random IP addresses, random ports,
I'd say remove it, and instead rely on the "Skype VOIP Checking Version"
rules to catch at least some installs of it.
An alternative could be to alarm upon access to skype's login server.
The file C:\Documents and Settings\All Users\Application
Data\Skype\shared.xml (skype 1.0) contains these infos:
<EventServers>
<DirectlyConnected>1</DirectlyConnected>
<LastTCPServer>80.160.91.28:12350</LastTCPServer>
<LastUDPServer>212.72.49.142:12350</LastUDPServer>
</EventServers>
<LoginServers>
<DirectlyConnected>1</DirectlyConnected>
<LastTCPServer>195.215.8.141:33033</LastTCPServer>
</LoginServers>
I don't know how skype uses these infos, but I guess it sometimes uses them.
This file also contains the p2p hosts cache (random ip addresses & ports)
alert ip $HOME_NET any -> 195.215.8.141 any (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP Login"; classtype:policy-violation; sid:9999988; rev:1;)
alert tcp $HOME_NET any -> any 33033 (msg:"BLEEDING-EDGE P2P VOIP Skype
VoIP Login"; classtype:policy-violation; sid:9999989; rev:1;)
alert udp $HOME_NET any -> any 33033 (msg:"BLEEDING-EDGE P2P VOIP Skype
VoIP Login"; classtype:policy-violation; sid:9999990; rev:1;)
alert ip $HOME_NET any -> 80.160.91.28 any (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP Event"; classtype:policy-violation; sid:9999991; rev:1;)
alert ip $HOME_NET any -> 212.72.49.142 any (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP Event"; classtype:policy-violation; sid:9999992; rev:1;)
alert tcp $HOME_NET any -> any 12350 (msg:"BLEEDING-EDGE P2P VOIP Skype
VoIP Event"; classtype:policy-violation; sid:9999993; rev:1;)
alert udp $HOME_NET any -> any 12350 (msg:"BLEEDING-EDGE P2P VOIP Skype
VoIP Event"; classtype:policy-violation; sid:9999994; rev:1;)
alert ip $HOME_NET any -> 198.63.210.250 any (msg:"BLEEDING-EDGE P2P
VOIP Skype VoIP web site"; classtype:policy-violation; sid:9999995; rev:1;)
alert udp $HOME_NET any -> 64.141.3.65 53 (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP dns"; classtype:policy-violation; sid:9999996; rev:1;)
alert udp $HOME_NET any -> 195.50.213.37 53 (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP dns"; classtype:policy-violation; sid:9999997; rev:1;)
alert udp $HOME_NET any -> 80.160.91.4 53 (msg:"BLEEDING-EDGE P2P VOIP
Skype VoIP dns"; classtype:policy-violation; sid:9999998; rev:1;)
alert udp $HOME_NET any -> any 53 (msg:"BLEEDING-EDGE P2P VOIP Skype
VoIP dns"; content: "|05|skype"; depth: 50; classtype:policy-violation;
sid:9999999; rev:1;)
whois reports these netblocks:
inetnum: 212.72.49.128 - 212.72.49.159
netname: SKYPE-NL
inetnum: 195.215.8.0 - 195.215.8.255
netname: TDC-HOSTING-OEBRO
inetnum: 80.160.88.0 - 80.160.91.255
netname: TDC-INTERNET-SERVERCAMP-OPA
Nom : skype.com
Address: 198.63.210.250
nslookup -type=ns skype.com
skype.com nameserver = ns4.joltid.net
skype.com nameserver = ns5.joltid.net
skype.com nameserver = ns.joltid.net
ns5.joltid.net internet address = 64.141.3.65
ns.joltid.net internet address = 195.50.213.37
ns4.joltid.net internet address = 80.160.91.4
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