An open network is one that anyone can access, and many open networks let devices connect without a password. That convenience comes at a cost: because the network is open and often unencrypted, the data travelling across it is not protected.
When data is unencrypted, it travels in a form that anyone on the same network can read. A person sitting nearby with the right software can intercept that traffic and view it. Anything sent in plain text, such as a password typed into a login page, card details entered at an online checkout or a private message, can be captured and then reused to sign into your accounts or spend your money. For example, signing into your email over an open network in a shopping centre could let someone else copy your username and password as you type them. Stolen data has value, so it can also be sold on for financial gain.
An open network is easy for a malicious user to join, and once they are on it they can introduce malware onto a connected device. If that software installs successfully, it can corrupt files, damage the operating system or give the attacker control of the device and everything stored on it.
An ad hoc network is created directly between devices, so it is open in much the same way and is easier for a hacker to reach. Because no server controls who joins, security is managed by each device individually rather than centrally. Each person has to configure and protect their own device, and there is no single point where an administrator can block intruders or apply rules for everyone. That is why an ad hoc network with no central security is less safe, not more.
Pearson BTEC Digital Information Technology · Communication technologies