Wireshark is powerful tool that acts as a network eavesdropping utility for intercepting and analyzing both wired and wireless network traffic, and like any good tool can be used both for good and for ill.
The only way to foil this sort of snooping is by encrypting your network transmissions, and even then, because your packet headers cannot be encrypted, a snoopy person can still glean information such as IP addresses, encryption certificates, and network protocols. If you’re wondering why packet headers cannot be encrypted, think about it – routers need to read the headers so they know where to send the packets. Encrypting headers would be like encrypting the addresses on paper letters.