If @xper or @Tripredacus can bring themselves to take my comments seriously and investigate the MSFN server, they must do so very thoroughly, as the infection is more or less hidden or invisible.
In IT security, this phenomenon is known as "cloaking" (making content visible only to search engines) or shadow injection.
Here is an attempt at a factual, technical explanation of why this Thai content was invisible to visitors in their browser:
1. The phenomenon of "cloaking" (the user-agent switch)
The malware that has infected the forum checks the user agent (the visitor’s identifier) every time a page is loaded:
If you, as a normal user, visit the site using a browser, the server sees: “Ah, a normal person.” The script ignores you and delivers the completely clean, familiar MSFN forum. You don’t see a single spam post.
When the Google bot (Googlebot/2.1) visits the page, the malicious script recognises the identifier and switches over. It injects the Thai keywords, casino text and spam links into the HTML code specifically for this one bot.
As the Google bot sees this, it stores it in its index. As a user, you won’t notice a thing until you search for MSFN via Google and wonder about the hieroglyphics.
2. Exploiting the internal search function (URL injection)
Many forum software packages have a vulnerability in the way they process search queries. Bots send millions of specially crafted search queries containing Thai terms to MSFN.
The forum then dynamically generates a page with the title: "Results for the search: [Thai casino link]" . The bots copy this generated URL and link to it en masse on dubious external websites. When Google follows these links, the bot lands on MSFN on a Thai results page (which exists for it) that never appears in normal forum operation or in the sub-forums.
3. Hidden system files (database level)
Often, the attackers do not embed themselves in the visible text area of the threads, but instead modify a deep-level system file (such as the .htaccess file on the server or a core file of the forum software). This file intercepts the data stream and adds the Thai code in the background – but only if the request comes from a search engine.
Conclusion:
There’s no need to worry: the forum on MSFN that people use and love every day is clean in terms of its content. The database of genuine threads remains unaffected.
This is a purely technical "parasite infestation" running in the background, specifically optimised to deceive the Google bot and exploit MSFN’s reputation (domain authority) for illegal advertising purposes. As the administration doesn’t see this malicious code during normal forum operations, it usually only comes to light when Google’s hammer strikes mercilessly in the wake of a core update.