Anyone with the knowledge can look at your data. Using a method known as 'spoofing' they can even inject fake data into a legitimate stream. These problems come about because of the way that internet protocols interact. To overcome these difficulties ssh was devised. Encryption is using codes to protect the packets of data while in transit.
Authentication is a process for verifying if a.packet of data or a connection is valid.
There are ssh clients for most other operating systems too. By using Linux as a server you can provide ssh level security for all your network use. Here are some tools that log to files. Check these tools are correctly installed then if you suspect an attempted break in, check the logs. The main problem with logging events is that one tends to end up with too much data.