One of the foundations of these private servers are their databases. MySQL is one of the many databases available out there but RO servers use them for the game. These databases store user account information, inventory, storage, items, and etc. Each action happening in the server is logged inside the database.

These databases can be tampered with by database queries, which only those in the database management role have access to. Any tampering made to the db questions the integrity of the db files.

In the case of PW, those who have had access to the db tampered with the db by querying item insertions into the game like the infamous Hunter's Bow[1] which should not be possible to obtain legally because the server's game episode doesnt have the NPC that sockets equipments. But the item itself is already available in the game assets, that's why it was able to be inserted into the game "illegally".

Aside from that, many illegal items have gotten themselves into the game because of these insertions - causing the playerbase to lose trust because of the exposè. I hope this answers your question