Wi-Fi specifically.
WHAT TO SET
A strong unique wireless password Current encryption A network name that does not identify your business or router model
THE NAME POINT
A network named after your business tells anyone nearby whose it is.
WHAT NOT TO DO
Leave a network open Use an outdated encryption standard Share the password broadly
THE SHARED PASSWORD PROBLEM
A password known to former staff, visitors and contractors is not a control.
Change it periodically.
GUEST NETWORKS
A separate network for visitors, isolated from your business devices.
Most routers offer this.
WHY IT MATTERS
A visitor's compromised laptop should not reach your systems.
FOR CUSTOMER WI-FI
Definitely separate, and consider what obligations offering it creates.
WHAT TO CHECK
Which devices are connected.
WHAT TO DO IF YOU SEE SOMETHING UNRECOGNISED
Change the password and reconnect your own devices.