 The attacker then observes the change in size of the compressed request payload, which contains both the secret cookie that is sent by the browser only to the target site, and variable content created by the attacker, as the variable content is altered.When the size of the compressed content is reduced, it can be inferred that it is probable that some part of the injected content matches some part of the source, which includes the secret content that the attacker desires to discover.Divide and conquer techniques can then be used to home in on the true secret content in a relatively small number of probe attempts that is a small multiple of the number of secret bytes to be recovered.