Editing Transport Layer Security (section)

====Truncation attack====
A TLS (logout) truncation attack blocks a victim's account logout requests so that the user unknowingly remains logged into a web service. When the request to sign out is sent, the attacker injects an unencrypted [[Transmission Control Protocol|TCP]] FIN message (no more data from sender) to close the connection. The server therefore does not receive the logout request and is unaware of the abnormal termination.<ref name=register20130801>{{cite web|title=Gmail, Outlook.com and e-voting 'pwned' on stage in crypto-dodge hack|url=https://www.theregister.co.uk/2013/08/01/gmail_hotmail_hijacking|work=The Register|access-date=1 August 2013|author=John Leyden|date=1 August 2013|url-status=live|archive-url=https://web.archive.org/web/20130801193054/http://www.theregister.co.uk/2013/08/01/gmail_hotmail_hijacking|archive-date=1 August 2013}}</ref>

Published in July 2013,<ref>{{cite web|title=BlackHat USA Briefings|url=https://www.blackhat.com/us-13/briefings.html#Smyth|work=Black Hat 2013|access-date=1 August 2013|url-status=live|archive-url=https://web.archive.org/web/20130730124037/http://www.blackhat.com/us-13/briefings.html#Smyth|archive-date=30 July 2013}}</ref><ref>{{cite thesis|last1=Smyth|first1=Ben|last2=Pironti|first2=Alfredo|title=Truncating TLS Connections to Violate Beliefs in Web Applications|journal=7th USENIX Workshop on Offensive Technologies|date=2013|url=https://hal.inria.fr/hal-01102013|access-date=15 February 2016|url-status=live|archive-url=https://web.archive.org/web/20151106110117/https://hal.inria.fr/hal-01102013|archive-date=6 November 2015|type=report}}</ref> the attack causes web services such as [[Gmail]] and [[outlook.com|Hotmail]] to display a page that informs the user that they have successfully signed-out, while ensuring that the user's browser maintains authorization with the service, allowing an attacker with subsequent access to the browser to access and take over control of the user's logged-in account. The attack does not rely on installing malware on the victim's computer; attackers need only place themselves between the victim and the web server (e.g., by setting up a rogue wireless hotspot).<ref name=register20130801/> This vulnerability also requires access to the victim's computer.
Another possibility is when using FTP the data connection can have a false FIN in the data stream, and if the protocol rules for exchanging close_notify alerts is not adhered to a file can be truncated.