Is high-security space safe? Can other players attack me there?

High-sec is safer, not safe.

CONCORD, the police NPCs, will always destroy a player who illegally attacks you in high-sec, but they arrive after the attack. Some players accept that loss on purpose to destroy a valuable target. This is called ganking.

How to avoid being a target:

• Do not carry expensive cargo in a weak ship.
• Do not leave your ship sitting on autopilot through busy systems.
• Fit for what you are doing, and do not fly what you cannot afford to lose.

Most new pilots who are careful are rarely ganked.