When you are filing a complaint to the police, it is important for you to gather all the necessary digital evidence and not only to copy the content of the message in question. It is often not simple, as it requires technical knowledge and patience, for which few people upset by the attack can have nerves. If you can't deal with it, call a friend, colleague or family member for help. They can also record evidence of an attack, but also deal with your account on the platform on which the attack is taking place. The documentation should contain material evidence of the attack and be classified so as to facilitate the search. Using a spreadsheet can be convenient, as attacks can be sorted by time, location, cause, duration and type of attack, reports filed on the platform, and response. This is all important information for lawyers, police, further investigation and court proceedings. Try to identify the type of attack, because some forms of online threats are still unknown to the general public, and sometimes even to the police. This will help the investigators to better understand what happened and how to look for the perpetrators.
First, you should provide relevant links or URL addresses in their integral form, i.e. if the attack occurs on social media, then you should provide an integral link of the account which sent you a threat. Then, you should save a copy of the message in an integral form containing metadata, i.e. email headers.
Furthermore, it would be good to make a screenshot/print-screen of the message, image or a video included in the incident. On the other hand, if there are several segments of the incidents - you are facing-multiple SMS-s, messages received via an application on a computer or phone, etc. - you should make a screenshot of each one or possibly make a video of the entire process.
In addition, if the harassment occurs through phone communication, then the report should contain call logs issued by the phone operator because they contain the time of the call and the number from which the call was made, which may make further investigation easier. Also, you can turn to a Computer Emergency Response Team in your country, which may provide technical support and mitigate the damage, or state bodies in charge of investigating cybercrime .