WordPress tries to guess the permalink?

Hi,

I’m working on the new version (WP) of an old news site (PhpNuke), so I have to redirect the indicized old URLs to the new ones.
What I’ve done: I’ve added some lines at top of /mytheme/404.php that check for the http call, parse it and redirect to the new pretty URLs.

The problem: if the old URL contains “News” (ie: https://my.website.com/modules.php?name=News&file=article&sid=17590) WP doesn’t even look at 404.php at goes directyl to https://jugo3.comunicrea.com/archivio/news-a-pagamento-si-comincia-dal-times?file=article&sid=17590 which is an article that in the title (and so in the permalink, too) contains the word “News”.

Same thing with an URL with a different “sid”.

If you strip off the word “News” from the old URL (ie: https://my.website.com/modules.php?name=&file=article&sid=17590) WP looks into 404.php and there the lines of code I’ve added make the rest of job…and everything is ok.

So…is it possible that WP, when an URL doesn’t exists, tries to guess the correct one?
I’ve no redirect plugin installed.

Thanks!