Skype is a free internet calling (VoIP) program that also allows video chats and instant messaging. Securing Skype involves enhancing privacy options, but you can also use Microsoft EMET for protecting the program from zero-day bugs (but remember to turn off the EAF protection for skype.exe and skypePM.exe).
First, you must be logged in to Skype. Then open Tools menu and click Options.
In Skype - Options window, expand the Privacy tab and click Privacy settings.
First, select the Only allow people on my Contact list to contact me option to prevent stalking and unwanted calls or Instant Messages (IMs). Beware - this option might not be suitable for businesses providing support via Skype.
Then click the Show advanced options button.
Now set the Automatically receive video and share screens with option to no one. You should never send or receive videos and share screens automatically - this can be misused by malware.
Set Allow IMs from to people in my Contact list only. Again, this prevents unwanted messages and stalking, while business support people might be more open about this setting.
One of the most important privacy settings in Skype is the Keep history for. This does not include call and messaging history on your own computer only (like in Windows Live Messenger), Skype automatically uploads all stored history to its own servers and synchronizes the whole history with all computers you use Skype on. All your Skype history gets stored and will be easily accessible on public computers, friends' computers, etc after you login to Skype from there. This is a major privacy threat, not to mention possible leakage of your own personally identifiable information. You should always select no history from the combo box (the default is forever).
To complete the erasing of your Skype history, click Clear history. Make sure no conversation is open at this time!
Then click Delete in the Delete history dialog.
Make sure the Allow my online status to be shown on the web check box is cleared. You should not reveal the status publicly unless you provide business support services.
Then clear the Allow Microsoft targeted ads, including use of Skype profile age and gender check box. This is once again all about monitoring and storing your online behavior and customizing the ads shown to you.
Those who want to be extra private, can also disable the Accept Skype browser cookies option and click Clear Skype cookies.
To manage blocked people in Skype, click the Blocked contacts tab. Here you can either select blocked person and click Unblock this person, or select a name from your Contact list and click Block this person.
Then click to expand the Notifications tab. Click Alerts & messages. Then clear the Promotions check box in Show messages about setting. This reduces the number of ads displayed.
And finally, expand Advanced tab and click Automatic updates. Verify that the button reads Turn off automatic updates. If it states "Turn on automatic updates", click it and then click Continue or Yes in User Account Control prompt.
This will keep Skype updated. Sure, you can also use free Secunia PSI for the job.
Click Save to apply changes.