If we don't study computer information security in depth, but just fiddle with it on the surface and use some software, then mathematics is not so important in information (network) security. However, if you want to study computer information security in depth, explore the essence of information security, such as information hiding, password, data recovery and so on. Then mathematics is very, very important. If a computer information security student can't learn mathematics, he must be making up numbers. For example, the security of passwords, from symmetric encryption in the past to asymmetric encryption now, is mathematics, especially discrete mathematics; Computer viruses also need math, not that you can program languages.
If you want to engage in information security in depth, I suggest you look at the mathematics textbooks in the university, read advanced mathematics first, and then read linear algebra, number statistics and discrete mathematics. There are also teaching materials about information security (such as PKI, computer virus, cryptography, etc. ), there is to understand the operating system.