system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - How do hacker groups take down websites "on demand"?

More precisely the Russsian government websites. How come the Anonymous decided to attack and actually be successful in bringing it down withim few hours since the announcement and then supposedly leak some data off it?
Are they good in quickly finding holes or the websites, even government ones, are poorly protected/coded?
gpt
When some vulnerability is found and kept secret, it's called a 0day which literally means 0 days since it was known.  Lots of hackers have a stack of these or buy/sell them to other groups. 95% of the time it's not target specific, but a way to access a large portion of targets, but after using the exploit it will end up being publicly known and patched by vendors.

Government are also not great at staying up to date with the latest patches so it's possible there was a known flaw that was not patched.