Keeping your text entry fields secure

Question

I've noticed over the past few days someone has been entering text like the following into my comment fields :

<a href="http://www.distritofederal.df.gov.br/003/00301009.asp?ttCD_CHAVE=101732&lorcet">lorcet</a>  
unendurable imperfections <a href="http://www.distritofederal.df.gov.br/003/00301009.asp?ttCD_CHAVE=101746">phentermine side effects</a> 
eolith acidimeter 

What is this person trying to achieve, and is there anything I need to do to ensure they don't do anything malicious through my text entry fields?

EDIT

It looks like this site belongs to the Brazilian government. Other sites that have been linked don't even exist. Hence I am a bit skeptical that this is just link spamming..

Answer 1

They get links to their site, which is good for ranking high in the search engines.

And additionally they gain exposure, since visitors of your site might follow these links..

As @mark mentioned, it could very well be of malicious intend if the linked site is 'bad'

More important is to make sure that your site does not allow in the comments all types of tags. If you do, then someone could post a comment with a <script> tag that could load some malicious code to the browser of your sites visitors, and it would seem like you are the responsible party.. and your visitors would be exposed ..

Answer 2

One possibility is that this is enticing people to follow a link that includes some kind of exploit in the query string. I don't see anything that looks like an exploit in the example posted in your question though.

Another possibility is that the server that is being linked to has been compromised and is now being used by the spammer to host sites of which the server's operator may not approve.

As per other answers, it could also be someone doing generic link spamming, although it seems unlikely that a government department would use (or at least endorse) this technique. It may be someone testing out a link spamming system before they use it for real.

Answer 3

That's just link spam.

What they are trying to achieve is to get a lot of links to their website.

That helps them with their search engine optimization.

Looks like they have a nice "random word generator".

EDIT

Maybe they're testing out their new link spamming machine on you.