Understanding the BREACH Attack and Content Length

Understanding the BREACH Attack and Content Length

The BREACH attack is a Side-Channel attack. You need some way to access the side channel.

On page 13 of the presentation, you can see what BREACH needs the attacker to set up:

1. A web server serving the site the browser visits.

2. A callback where the javascript on the victim’s browser notifies the attacker that the request completed, giving time information about when the packets with the currently tried string went through.

3. A MITM for monitoring the length of the sent packets.

So, in other words, you need access to the wire.