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).
Please note that in Windows 8 and 8.1, there is a Windows Store (aka Metro/Modern UI) Skype app. If you are using it, jump to the configuring Skype app section.
First, you must be logged in to Skype. Then open Tools menu and click Options. Keyboard shortcut for this is Ctrl+Comma.
In Skype - Options window, expand the Privacy tab and click Privacy settings.
First, select the people on my Contact list only option in the Allow calls from section to prevent stalking and unwanted calls. Beware - this option might not be suitable for businesses providing support via Skype.
Set the Automatically receive video and share screens with section to no one. You should never send or receive videos and share screens automatically - this can be misused by malware.
Choose people in my Contact list only in the Allow IMs from section. 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 current PC only, because Skype automatically uploads all stored history to its own servers and synchronizes the whole history with all computers and devices you use Skype on. Your whole Skype is easily accessible on any public computer, friend's computer, etc after you login to Skype from there. This is a major privacy threat, not to mention possible leakage of your 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.
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 to your Skype settings.
To change settings for Skype app, launch it and then use keyboard shortcut Windows Key+I to open Settings charm. Touch-screen users can swipe in from the right side of screen and tap Settings.
Click or tap Options.
First, set the Incoming video and screen sharing setting in Video section to Ask. You should never send or receive videos and share screens automatically - this can be misused by malware.
Continue to Privacy section and choose Only my contacts from the Who can call you dropdown. This prevents stalking and unwanted calls, but it might not be suitable for businesses that provide online support.
Next, select Only my contacts from the Who can send you instant messages combo box.
Skype for modern Windows app stores your call and instant message history only on the device you are using. If you want to delete your tracks, click or tap the clear history button (see picture above).
The action will be confirmed, click or tap the same button again.
Click or tap the Back button (←) on top left of Settings charm and open Permissions.
Here you can choose if Skype app can use your Microphone and Webcam. For video chats, you need to leave these sliders to On position.
In case you do not like Skype notifications, you can turn both Notifications (aka Toasts) and Lock screen notifications off. The latter will also prevent the app from running in the background.
That's it for Skype app settings. To close Settings charm, click or tap outside the charm.