It is illegal to try and attempt to gain unauthorized access to someone else’s account. Under Criminal Justice (Offences Relating to Information Systems) Act 2017 section 2. A person who, without lawful authority or reasonable excuse, intentionally accesses an information system by infringing a security measure shall be guilty of an offence. Further under section 8 (1) (a) you shall be liable on summary conviction, to class A fine or imprisonment for a term not exceeding 12 months or both, or under section 8 (1) (b) on conviction on indictment, to a fine or imprisonment for a term not exceeding 5 years or both.