A successful mug works like other attacks in that it sends the target to the Hospital, but it also steals cash. The attacker takes 10% of the target's unprotected cash on hand. Cash in the bank and in property vaults cannot be stolen by a mug.
Mug cash gains can be increased with the Calm Negotiator Achievement reward: +5% per level, up to 10 levels (50%). That scales the base 10% take, so at maximum Calm Negotiator a mug steals 15% of unprotected cash on hand.
A successful mug also hospitalises the target for roughly 35 minutes — about 15 minutes less than a standard attack hospitalisation — and awards roughly half the Reputation of a normal attack win.
Mug Protection stops someone from draining all of a player's cash on hand by repeatedly mugging them in a short window. It is a decaying cash shield, not full immunity to mugs.
After a successful mug that steals cash, the target's Mug Protection is set to the cash remaining on hand after the steal, and the protection timer starts at 100%.
Only cash above the current effective shield can be mugged. The steal is then 10% of that unprotected excess (plus any Calm Negotiator bonus).
Cash gained after the last mug (jobs, bank withdrawals, trades, and so on) does not raise the shield. It sits above the shield as unprotected excess and can be stolen normally.
If a later mug steals £0, the existing shield and timer are left unchanged.
If a later mug does steal cash, the shield is refreshed to the new remaining cash on hand and the decay timer resets to 100%.
The shield's effectiveness starts at 100% and falls by 0.0023 percentage points per second (about 0.138 per minute). It reaches 0 after roughly 12.1 hours. While decaying, only the remaining percentage of the original shield amount still protects cash.