You can hack a portal up to four times in a row. After four hacks, the portal “burns out”.

If you try to hack a fifth time, the game will tell you “Portal burned out! It may take a significant amount of time to re-set.”

How long does burn-out last?

Burn-out lasts four hours.

The four-hour timer starts from your first hack. If you hack four times, starting at 12-o’clock, you can hack again starting at 4-o’clock.

How can I get more hacks in a row?

Deploying a heatsink mod instantly clears the burn-out timer, so you can start hacking again straight away. Heatsinks re-set the burn-out for you, and only you - other agents don’t benefit. (Details: Heatsinks).

Deploying a multi-hack mod lets you hack a portal more times in a row, before you burn it out. Multi-hacks benefit all agents - you, your team, and the other team. (Details: Multi-Hacks).