For several months, I had been getting mysterious instant messages from strangers. Somebody with an unfamiliar username ending in -coho would IM me "hey" or "who's this" or some bit of nonsense. I would typically answer "Do I know you?" or "Who's this?" Then the other person would answer: "What are you talking about? You IM'd me!" They turned out to be as equally baffled and suspicious as I was. It took me a while to conclude these people were not scammers or pranksters but victims of the prank too. Eventually, I searched for "coho" and "IM" and found the answer: It's an annoying but apparently harmless Web bot. It seems to be a social experiment, or a prank. Sometimes the IM-bot goes by names that are variations on -trout and -salmon. Mine have been strictly cohoe.

As best anyone can tell, the bot was created by something called Project Upstream, although its first victims on LiveJournal traced it to something called TheGreatHatsby. They typically cite a Wikipedia entry that has since been deleted. There's a fresh take at Mahalo Answers.

It appears that the prank first targeted IM handles harvested from LiveJournal blogs and other sites, before targetingTwitter users. Some people have been frightened that they were being stalked online, while others suspected a virus, spammers or hackers. Complaints to AOL proved fruitless.

Project Upstream describes itself this way:

Project Upstream is an organization dedicated to promoting social ideals through the use of exciting new technology. Our most well-known service is our swarm of robotic fish, which connects AIM users to each other. Robotic fish connections occur spontaneously, and also by request. If you would like to partake in the robotic fish experience, you are encouragd to enter your AIM name below. Your request will be filled as soon as possible.

So, first of all, coho can't spell. And second, there's no verification system. Presumably people can prank unsuspecting people. And what if you don't want to be part of the robotic fish experience? You won't find the answer on that page. But several of the coho-bloggers linked above described a procedure for opting out using a simple command -- $optout.

Once I found out the cause of the IMs, they seemed less alarming. I imagine there are even people who use these pings as an opportunity to goof on random strangers <a href="">with wacky nonsense. (You show up to the other user as something-coho.)

I hadn't decided whether I would opt out the next time I got a bite. And then I didn't hear from one for weeks and weeks and nearly forgot about it, until Monday. HotHeadedCoho interrupted a critical task, and I decided I'd had enough. Plus, I was curious to see if the $optout command actually worked:

3:33 hotheadedcoho I hope your day is wonderfully amazing, just like you! 3:34 [ME] $optout 3:34 hotheadedcoho is now known as HotHeadedCoho. 3:34 HotHeadedCoho OPERATOR: Are you sure you want to opt-out? If you do, you will *never* be contacted again on the account "[ME]". There is *no way* to opt back in and undo this. If you are sure, type "$optout F38A". Remember, this is permanent and irreversible! 3:34 [ME] $optout F38A 3:34 HotHeadedCoho OPERATOR: You have opted out. The accout "[ME]" will *never* be contacted again. Good bye! Feel free to email projectupstream@gmail.com with feedback, comments, complaints, etc.

Now we'll see if this actually works.