Skype
Sensepost Maltego Toolkit: Skyper
Collecting and performing Open Source Intelligence (OSINT) campaigns from a wide array of public sources means ensuring your sources contain the most up to date information relating to your target. Skype, with over 300 million users, can be a vital source if used correctly.
The above graphic shows over 70 million active members and over 500 million users that have registered!.
As with all things online, many users leak sensitive information about themselves that those with the right skills, could harvest.
Client Side Fingerprinting in Prep for SE
On a recent engagement, we were tasked with trying to gain access to the network via a phishing attack (specifically phishing only). In preparation for the attack, I wanted to see what software they were running, to see if Vlad and I could target them in a more intelligent fashion. As this technique worked well, I thought this was a neat trick worth sharing.
First off the approach was to perform some footprinting to see if I could find their likely Internet breakout. While I found the likely range (it had their mail server in it) I couldn’t find the exact IP they were being NAT’ed to. Not wanting to stop there, I tried out Vlad’s Skype IP disclosure trick, which worked like a charm. What’s cool about this approach is that it gives you both the internal and external IP of the user (so you can confirm they are connected to their internal network if you have another internal IP leak). You don’t even need to be “friends”, you can just search for people who list the company in their details, or do some more advanced OSINT to find Skype IDs of employees.
Skype Passive IP Disclosure Vulnerability
When performing spear phishing attacks, the more information you have at your disposal, the better. One tactic we thought useful was this Skype security flaw disclosed in the early days of 2012 (discovered by one of the Skype engineers much earlier).
For those who haven’t heard of it – this vulnerability allows an attacker to passively disclose victims external, as well as internal, IP addresses in a matter of seconds, by viewing the victims VCard through an ‘Add Contact’ form.
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