Given the way Twitter works – its fairly open API and the ease of creating Twitter accounts (Twitter doesn’t require you to have a valid email address when creating a new account), it is surprising there isn’t more spam on Twitter than there currently is. We have all starting reading the reports on Twitter spam attacks or celebrity Twitter accounts being hacked or how big the spam problem on Twitter will get! With more and more business (and individuals) taking to Twitter to promote their ventures (and potentially their scams), expect spamming on Twitter to eventually explode! After all, by some claims 90% of all email is spam. Here is my attempt at a short but comprehensive list of the types of Twitter spam and abuse that is going on:

General Spamming and URL Shortners
It is becoming a common practice for individuals use their real or fictitious accounts to shamelessly promote their services to the general public via Twitter. This sort of spam is be expected, after all, one man’s (or woman’s) spam is another man’s (or woman’s) “business opportunity”! What makes spam on Twitter worse are the URL shortners!Become many users shorten their links with a URL shortner to get the most of Twitter 140 character limit, sometimes innocuous looking links point to viruses, trojans, pornography, or scams! It is impossible to tell, until you click the link.

Hash and Trend Spamming
This builds on generally spamming to make it more effective (or sometime targeted). This form of spam takes advantage of trending topics on Twitter by adding a hash tag to particular keyword in a tweet. Recently, for example spammers have been taking advantage of the sad death of Michael Jackson by adding #MJ and #MichaelJackson to their tweets. The same sort of thing has been going on with the #Iranelections and other popular trending topics.  By adding trending topics or keywords to their tweets, spammers get their tweets to show up more often in popular (or targeted) searches. This has sometimes forced Twitter to temporarily disable trend searching on its site.

@username Spamming and Tweetjacking
This takes advantage of the popular practices or reply to/retweeting over peoples tweets. This common form of Twitter spam involves spammers replying to your @username, which then causes the Tweets to show up in your timeline (and may cause you to read it). This has quickly evolved into the practice of Tweetjacking. Here someone replies to or re-tweets a post you made, except they substitute your shortened URL in the post (http://tinyurl.com/good, i.e.) with another shortened URL that points to porn or scam site (http://tinyurl.com/bad,i.e.).

Twitter Account Hijacking
This involves hackers breaking into your account and using it for their own purposes (warning: avoid simple or obvious passwords on your Twitter account). Spammers hack into a reputable account (presumably with a lot of followers) and use it to send out spam. Accounts of popular Twitter users such as former Mac evangelist (or more recently investor) Guy Kawaski and even Britney Spear’s (TwitPic accounts) have been recently hacked! The list of celebrities who have had their accounts hacked continues to grow! (Lindsay Lohan, Barack Obama, Britney Spears, Fox News, ie). In fact this and the legal problems that follow has promoted Twitter to launch verified accounts.

Follower Inflation, “Follower Services” and Related Spam
The Twitter economy is based in part on the number of followings you have. Since creating an account is relatively easy, some has introduced automation to amass hundreds or thousands of fake followers! Some of these “spammers” have gone on to try and sell their services or accounts to the highest bidders! Spammers use this and related techniques to propagate general spam and grow their spam network.

Twitter Harassment
Not really spam but definitely a form of social networking abuse has prompted Twitter to put out and try and enforce a Twitter Harassment Policy (some have claimed this is not enough). Individual can and do get harassed on Twitter. Some have been harassed professional views, celebrities have complained about being stalked/harassed on Twitter and you can expect the same time of harassment that goes on social networks such as MySpace to rear its ugly head!

Dealing with Twitter Spam and Abuse

1. Be Careful Who You Follow
   Tools like Twitchuck allow you check to see if @username appears to be a spammer by analyzing metrics such as their following to follower ratio, number of posts and other metrics. A lot of spammers try and capture followers (and potentially gain more credibility and exposure) by very quickly following as many people as they can. Consider blocking these individuals.
2. Be Careful What You Click
   As I mentioned earlier, you can never be sure exactly what you are clicking on in Twitter (and other services) where true URL addresses are hidden behind a URL shortner (such as tinyurl.com, bit.ly, i.e.). I think we should look to these services to add some level or protection or expect secure/spam-free URL shortner to appear. Unfortunately there isn’t any solution that provides complete protection (desktop spam filters help) since some of these messages may come from a friends hacked account! Definitely beware of clicking on links in tweets by people you don’t now or find in a general search!
3. Twitter Spam Filters and Techniques
   Expect these services (Clean Tweets, almost.at, TweetTornado, i.e. )to make an a big appearance shortly. But such a service would filter allow you to search for trends on Twitter or do simple searches while remove the tweets or known or suspected spammers. Expect more and more Twitter spam blacklists to appear (similar to those for email spam). There are also organization dedicating to identify spam fighting techniques on Twitter, check them out.
4. Abuse and Flagging Tools from Twitter
   A growing number of users are advocating that Twitter at tools that allow users to alert Twitter about abuse. I would expect that this will happen shortly. Abuse complaints already pour into Twitter’s support site. Twitter currently does suspend accounts “due to strange activity” so they are trying to get on top of the problem and ultimately they have the power (and best interest) to reduce spam on the service.  Twitter can easily start validating email addresses and adding “Flag User” or “Report Abuse” buttons on profiles and search results and I am certain they eventually will.