Lua Viruses aka Infection Viruses

A virus usually can be in a free model. They usually have weird names.

Some viruses contain "Vaccine".

Sometimes, a virus can copy the game you are in and give it to the other person, or just give the person access to your game. The virus can replicate itself into another part with its own code.

Viruses can be hard to delete, some viruses like Firespread.

List of viruses from Danger Level [bottom to top] But don't underestimate viruses, as some can get your IP.
 * Vaccine [Danger Level: 1] [Affect: spreads script to other part, easy to get rid of.] [Found in free models]
 * Plugin Virus [Danger Level: UNKNOWN] [Affect: Unknown as of now, have only heard of it, not seen the affect.] [Found in Plugins]
 * ROFL [Danger Level: 2-3] [Affect: Can cause scripts to not work because it renames everything in Workspace, StarterGui, etc [sometimes] to ROFL.] [Found in free models.]
 * Firespread virus [Danger Level 3] [Affect: Spreads fire across the map, which can cause lag to some players.] [Found in free model NPCs.]

For example, back near the 2014 times, there was a virus that went around called DETH.

DETH got into complicated lua, therefore getting into some code that could release the player's IP in the chat without filter.

DETH was later stopped near early 2015, as ROBLOX moderators, for a while, had started terminating accounts that made any model related to, and or using DETH.

DETH has not been seen since.

-- Advanced Virus Table