Most people today are using passwords in some form. There is also a fact that a great majority of people are not taking enough care about what kind of passwords they use, that is whether they have a simple or a complex password, nor do they think about the consequences of what would happen, should their password be compromised. What would be a sufficient password length in order to be safe for use? If we have an encrypted 7-zip file, what are the ways to attack this password, in order to crack it? How much time is needed for something like that, can it be done, and how can exactly do you approach cracking a 7-zip password? Answers to these questions were tried to be answered in this thesis, mainly being based on the practical measuring of time required to crack a password, using an application called hashcat. Hashcat supports many different attack modes on the hash of some password, but the three main ones used in this thesis are as follows: Brute-force/mask attacks, Dictionary attacks and Rule-based attacks. All three have been shown in great detail, and the time needed to prove whether an attack was successful or not was measured and explained.