Securing Instant Messengers
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Contents
Outline
Administrators often need to permit or block the use of IM (Instant Messengers) within Enterprises. While most use proprietary protocols and do not enter the Squid proxy at all, some have a port-80 failover mode, or may be explicitly configured to use a non-transparent proxy.
Applications
AOL Instant Messenger (AIM)
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Details
AIM natively uses TCP port 5190 and bypasses the Squid proxy. When configured to use an explicit proxy, it will use CONNECT tunneling to go through squid.
Squid Configuration File
# Permit AOL Instant Messenger to connect to the OSCAR service acl AIM_ports port 5190 443 acl AIM_domains dstdomain .oscar.aol.com .blue.aol.com acl AIM_domains dstdomain .messaging.aol.com .aim.com acl AIM_nets dst 64.12.0.0/16 205.188.0.0/16 http_access allow CONNECT AIM_ports AIM_nets http_access allow CONNECT AIM_ports AIM_domains
AOL
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid Configuration File
Configuration file to Include:
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AOL are known to change their Server IPs. The list below cannot be confirmed.
# AOL acl aol dst 64.12.200.89/32 64.12.161.153/32 64.12.161.185/32 acl aol dst 205.188.153.121/32 205.188.179.233/32 http_access deny aol
Gizmo Project (Pidgeon IM, Fring, Taler, ICQ, IRC, AOL)
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Gizmo Project include software to connect to a wide range of messaging protocols and VoIP services. This config does not include settings to block those IM which are not Gizmo Project provided services.
see Also:
If you know of other IM services available through Gizmo software please inform us.
Squid Configuration File
Configuration file to Include:
# Gizmo Project acl gizmo dstdomain .gizmoproject.com # Gizmo VoIP acl gizmo dstdomain .talqer.com .gizmocall.com .fring.com # Gizmo Chat acl gizmo dstdomain .pidgin.im http_access deny gizmo
ICQ ("I Seek You")
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid Configuration File
Configuration file to Include:
# ICQ acl icq dstdomain .icq.com http_access deny icq
MSN Messenger and Windows Live Messenger
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Details
Natively uses port 1863 and bypasses the Squid proxy. But when that has been locked down by the firewall admin it will failover to port 80 and enter Squid.
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Microsoft This is only confirmed to work with MSN Messenger and Windows Live Messenger if there is any other parts to the formal name its maybe another program completely with different access needs. |
Squid Configuration File
Configuration file to Include:
# MSN Messenger acl msn urlpath_regex -i gateway.dll acl msnd dstdomain messenger.msn.com gateway.messenger.hotmail.com acl msn1 req_mime_type application/x-msn-messenger http_access deny msnd http_access deny msn http_access deny msn1
Skype Access Controls
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid Configuration File
Configuration file to include.
- Since FTP uses numeric IPs the Skype ACL must be exact including the port.
Blocking
# Skype acl numeric_IPs dstdom_regex ^(([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)|(\[([0-9af]+)?:([0-9af:]+)?:([0-9af]+)?\])):443 acl Skype_UA browser ^skype http_access deny numeric_IPS http_access deny Skype_UA
- Recent releases of Skype have been evading the above restriction by not sending their User-Agent headers and using domain names. The following can be used to catch those installs, but be aware it will likely also catch other agents.
acl validUserAgent browser \S+ http_access deny !validUserAgent
Permitting
- This needs to be done before any restrictive CONNECT http_access controls.
acl numeric_IPs dstdom_regex ^(([0-9]+\.[0-9]+\.[0-9]+\.[0-9]+)|(\[([0-9af]+)?:([0-9af:]+)?:([0-9af]+)?\])):443 acl Skype_UA browser ^skype http_access allow CONNECT localnet numeric_IPS Skype_UA
Note that Skype prefers the port 443 which is by default enabled in Squid anyway so this configuration is only needed when you block HTTPS access through the proxy.
If you limit HTTPS access to known sites only, then permitting Skype will break that policy.
Trillian
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid Configuration File
Configuration file to Include:
- Trillian may change their Server IPs. If you know of others please inform us.
# Trillian acl trillian dst 66.216.70.167/32 http_access deny trillian
Yahoo! Messenger
Warning: Any example presented here is provided "as-is" with no support or guarantee of suitability. If you have any further questions about these examples please email the squid-users mailing list.
Squid Configuration File
Configuration file to Include:
# Yahoo! Messenger acl ym dstdomain .messenger.yahoo.com .psq.yahoo.com acl ym dstdomain .us.il.yimg.com .msg.yahoo.com .pager.yahoo.com acl ym dstdomain .rareedge.com .ytunnelpro.com .chat.yahoo.com acl ym dstdomain .voice.yahoo.com acl ymregex url_regex yupdater.yim ymsgr myspaceim # Other protocols Yahoo!Messenger uses ?? acl ym dstdomain .skype.com .imvu.com http_access deny ym http_access deny ymregex