Nowadays we use cyberspace heavily for work and play. In the physical world a degree of common sense about personal security comes naturally. In cyberspace "common sense" is unintuitive, but without it bad things can (and do) happen. Losing your wallet in the physical world is mainly inconvenient. But imagine what could happen if an untrustworthy stranger gains full access to everything you store and do using your phone. Just for starters, they could empty your bank account, delete your personal photographs, and extract embarrassing information from your social media activity. Worse, they can probably act as you in cyberspace for the foreseeable future.
It is wise to invest time acquiring cyberspace "common sense". Three guidelines go a long way:
Cyberspace is a wonderful place to work and play in. Staying safe is all about treating cyberspace with the common sense caution you apply in the physical world.
There are plenty of resources to help you develop a notion of common sense in cyberspace. Places to start include:
Get Safe Online: https://www.getsafeonline.org/
Get Cyber Safe: http://www.getcybersafe.gc.ca/index-en.aspx
Carnegie Cyber Academy (fun but worth a look): http://www.carnegiecyberacademy.com/
Prof. Keith Martin is from the Information Security Group at Royal Holloway, University of London. He has a particular expertise in cryptography and its applications within cyber security, and is author of the book Everyday Cryptography (Oxford University Press).