You've Been Hacked! A Valentine's Day Challenge (or… You've Got Sleepless Mail in Seattle)
Answers by Jay Swofford
1) Why hadn't the privacy settings in Tom's AIM client or the digital certificate in Meg's client encrypted their connection? The privacy settings do not affect encryption of transmitted data. The privacy settings (AIM 5.5) allow you to specify: - Who can contact me -- Allow all users to contact me -- Allow only users on my Buddy List -- Allow only the users below -- Block all users -- Block Internet users only -- Block the users below - Allow users to see... -- how long I've been idle -- that I am using a mobile device -- that I am typing a response - Allow users who know my e-mail address to find... -- My screen name -- Only that I have an account -- Nothing about me
We can assume Meg chose to Allow only Tom to contact her. We can also assume that she unchecked all the "Allow users to see..." boxes and selected "nothing about me" under the "Allow users who know my e-mail address to find".
However, none of these privacy settings affect data encryption between users. They also do not protect the user from keystroke loggers or trojans capturing data as it is typed by the user.
AIM certificates are explained at http://enterprise.netscape.com/products/aim/personalcerts/. The key paragraph on this page is: "AIM users can send and receive both encrypted and standard AIM messages. Messages exchanged with users that have security credentials are encrypted and messages with standard AIM users are not encrypted."
It didn't work because Tom did not have a certificate. Per the above web page: "When digital certificates are present, a message is digitally signed using the sender's certificate, encrypted using the recipient's public key and sent to the recipient. When the recipient receives the message, it verifies the sender's digital signature and decrypts the message using its locally stored private key."
As Tom did not have a digital certificate it was impossible to encrypt the traffic and AIM reverted to plain text messages. However, as Meg had a certificate, she was marked as secure in Tom's buddy list (the padlock icon Tom reported seeing).
2) How can Meg and Tom employ an encrypted protocol for communication using AIM? What other chat programs offer better security features?
Tom needs to purchase and install a personal certificate. Directions for importing the certificate into AIM 5.2 are included at the bottom of http://enterprise.netscape.com/products/aim/personalcerts/ with a flash demo using screenshot and animation at:
http://enterprise.netscape.com/products/aimsvcs/secure-cert_nosound.html. Then their messages to each other would be encrypted using the S/MIME email cryptographic standard. Once this is complete, under the text entry window, they should both see: "This IM conversation is encrypted and signed by <name>"
3) Given the evidence presented in the narrative above, which system had the attacker most likely compromised: Meg's computer, Tom's computer, a machine on a network sitting between Meg and Tom, or AOL's messaging system itself? Why?
Meg's computer, probably with a keystroke logger or AIM-specific logger. Logical evidence: The attacker was privy to what Meg typed but made no reference to Tom's portion of the threads (suggesting they can only see what is typed not what is read/displayed). Given that the attacker is trying to get her to dump Tom, they would have logically rather made Tom look stupid than just playing on Meg's email comment. If the attacker had compromised Tom's system, then they would have just sent Meg messages from Tom's account getting her to dump Tom. If the attacker had compromised AOL or the network they would have access to both sides of the conversation and would probably have made references to Tom's statements.
Technical evidence: If you look closely at the Ethereal trace you can see the keylogger/trojan at work. You will notice the following lines:
3 12.343676 10.1.1.4 64.12.25.109 AIM Message to: th4124 -> I think someone is listening to our chats! 5 2.208146 10.1.1.4 66.48.76.90 TCP 2696 > domain [SYN] Seq=1389461665 Ack=0 Win=16384 Len=42 10 6.567940 64.12.25.109 10.1.1.4 TCP Message from: th4124 -> Uh-oh! What should we do? 14 7.388246 10.1.1.4 64.12.25.109 AIM Message to: th4124 -> I dunno! I think we're in trouble... 16 3.130788 10.1.1.4 66.48.76.90 TCP 2697 > domain [SYN] Seq=1405600891 Ack=0 Win=16384 Len=37
Notice lines 5 and 16, as those are the logger sending data outbound. It is sending it outbound over TCP 53 in SYN packets. This is a good choice for the malware as TCP/UDP 53 are usually open for DNS lookups. Also notice that after line 10, there is no communication outbound, so we assume that Tom's inbound message was not captured (again pointing to a keystroke logger). Also notice that 66.48.76.90 does not return a SYN-ACK packet as would be normal under TCP handshake standards. Definitely suspicious!
Now lets look at the packet length. Packet 5 had 42 bytes of data and packet 16 had 37 bytes of data. This is exactly how many bytes of data are contained in packets 5 and 14 respectively when you remove the whitespace (most keystroke loggers and trojans will drop this as unnecessary to minimize data transfer).
So it looks like our culprit is located at 66.48.76.90 and definitely has control of Meg's machine. That address resolves to: w-wcom.netfirms.com. This is a site hosting facility: Netfirms, Inc., 5255 Yonge Street #800, Toronto, ON, M2N 6P4, Canada. Netfirms DNS server is 66.48.76.92, not .90, so it is unlikely that this is DNS traffic. With exact match on the byte sizes and data strings in AIM, we can be confident that whatever Meg sends in AIM is being logged or forwarded via this IP address.
The characteristics of this trojan/keystroke logger using TCP 53 are suggestive of the Muska backdoor family. Officially this family is listed as performing the following actions: Remote Access / Keylogger / Steals passwords / ICQ trojan / AIM trojan
4) What steps should Meg and Tom take next to deal with the bad guy and eradicate him from their lives?
Officially, Meg should contact local law enforcement. She should be able to get him charged with the following crimes at a minimum: Interception of Wire Communications - keystroke logger Unauthorized access to a computer system - installing logger and retrieving results Depending on what information was collected, how it used, etc. additional charges may be in order (identity theft, fraud, etc). Law enforcement could obtain the attackers real identity and IP used to send the message to Meg from AOL via a warrant. They should also work with Canadian law enforcement (additional laws may have been broken as the traffic crossed international boundaries, and local Ontario/Canadian laws come into play).