We are a mobile application development company.
Due to the security of Source Code and other files, we need to restrict Skype file transfer outside of LAN.
How to restrict Skype file transfer outside of LAN?
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It's exceedingly difficult to block Skype file transfers at the network level. They've designed it to use common ports (80 / 443) and proprietary encryption (albeit an extension to SSL) along with UPnP NAT holepunching to ensure absolutely minimal conflicts and setup issues. Remote file transfers go through supernodes as part of a P2P architecture, so it's not possible to blacklist a server to prevent the transfer.
You can disable the file transfer ability of Skype entirely, though. It's done via a registry key.
You may need to create this key first. Once you've found / created it, make a value called
DisableFileTransfer as a
DWORD and set its value to 1. This will completely disable file transfers within Skype. You may need to restart Skype or the whole computer for it to take effect.
After the transfers are disabled, you can use an alternative file sharing mechanism within your LAN, such as shared drives.
Note that you'll need to restrict access to the registry on those computers. Your users should run as limited accounts, and you should use group policy to deny access to administrative tools like regedit.
As another suggestion, are you only using Skype internally? If so, there are other platforms available that you could use for an internal experience that is very similar. Depending on your size, Microsoft Lync can be a nice (I'll be it, not free) option that behaves very similarly to Skype. There are also a number of open source and/or free options out there that provide text chat, but lack some of the more advanced features or ease of use that Skype has, but many of them can provide server side logging and prevent outside connections which is often a good best practice for internal communications unless outside connectivity is needed for a business reason.
You could use the lync product suite for skype like communication and you also can enable skype connectivity there. In this case you can disable the transfer of file types by using this settings. You also have some other possiblities for security there. The downside for lync are the license costs.