Cookies are messages that web servers pass to your web browser when you visit Internet sites. Your browser stores each message in a small file, called cookie.txt . When you request another page from the server, your browser sends the cookie back to the server.
It is mostly used by Web Server as an ID that was used to identify YOU from others. It is also used by program (eg. JavaScript) to store a temporal data used in the program itself.
The Cookie Law is a piece of privacy legislation that requires websites to get consent from visitors to store or retrieve any information on a computer, smartphone or tablet. Almost all websites use cookies – little data files – to store information in people’s web browsers.
Cookies that are sent over HTTP (port 80) are not secure as the HTTP protocol is not encrypted. Cookies sent over HTTPS (port 443) are secure as HTTPS is encrypted. So, if Facebook sends/receives cookies via HTTP, they can be stolen and used nefariously. That’s why you should always check for a green padlock right beside your browser’s url bar. A website without a green padlock is insecure and all data that are sent and received can be hijacked with Man-in-the-middle attack.
No, cookies are stored in txt files which will never cause any trouble to your device.