In retaliation for Anonymous' hack of the Syrian defense ministry webpage, a Syrian hacking force alleged to be called the "Syrian Electronic Army" struck back at Anonymous. How, you ask? They defaced Anonymous' pet project, the social network AnonPlus, by replacing the homepage with the message above, including gruesome pictures of burned and mutilated bodies. Anonymous' original hack was said to be in support of protesters in Syria and left a message encouraging the Syrian military to revolt against President Bashar al-Assad instead of supporting his suppression of the protests. The counter-hack attributed the current Syrian violence, depicted in the gruesome photos, to Syrian demonstrators instead.
The origin of the hackers was not mentioned on the defaced website. The attribution of this hack to the Syrian Electronic Army comes from a tweet by Citizen Lab, and the SEA are a recognized, public hacking organization, strikingly similar to Anonymous in their press and methods. They even have a bit of that Anonymous flavor to their message, stating that.
In response to your hacking to the website of the Syrian Ministry of Defence, the Syrian people have decided to purify the internet of [y]our pathetic website