iMPERVA has recently released a report on the attack patters followed by the Anonymous group. The report gives following insights on the Anonymous campaign

• The process used by Anonymous to pick victims as well as recruit and use needed hacking talent.
• How Anonymous leverages social networks to recruit members and promotes hack campaigns.
• The specific cyber reconnaissance and attack methods used by Anonymous. hackers. We detail and sequence the steps Anonymous hackers deploy that cause data breaches and bring down websites.

The report also provides some risk mitigation steps that organizations can follow to protect against attacks

The full report is available for download here