I've got a site that's been up and running sucessfully for about 6 to 8 months so far, and was informed by the recipient of the contact form submissions that about 10 days ago he started receiving gibberish contact form information about once every 2 to 3 days - the contact body has an anchor tag linking to an asian-language site (www.jinawa.com.cn) and appears to be an ad (unfortunately, it's in japanese or chinese, so it appears as gibberish and can't be read). But it's in the format that the php script I use to process the contact form builds, so it's not like somebody's sending an e-mail to the actual contact address - it's using our contact form.
What is this? Is it a random spambot, or is somebody trying to mess with my stuff, and should I be concerned about it? If it's something to be concerned about, what kind of security precautions can I add? I'd appreciate any advice/comments/information.
<edit> - I found this thread after some small searching and I think it explains what's happening.</edit>