One of the basis of today's radiological devices are computers and networks. The radiology department has a specific way of working, and there are standards such as DICOM for medical image records, PACS for archiving and communication, and HL7 for information exchange in the medical system. As radiology becomes an economically interesting branch, it becomes a target for cyber-attacks. At the same time, radiological systems contain a lot of personal data that may be of interest to individuals. The reasons for the attacks are often financial gain, but they can also be political, ideological or personal. The start of an attack can be physical access to radiological devices or network access. The DICOM files themselves can be the trigger of an attack. We divide attacks into those that directly affect patients, those that have an indirect impact, and those that affect the infrastructure itself. The most well-known types are Denial-Of-Service, malware, cryptographic attacks and making changes of device settings. When defending against cyber attacks, it is also important to secure communication by e-mail because it is common in malware attacks, and to keep programs on computers and devices updated according to the manufacturer's instructions, especially antivirus and firewall programs. The IT department of the radiology department should keep an eye on the accounts of all users and check the authorizations according to the workplaces so that there is no misuse. Networks must have access restrictions and division according to workplaces and purposes in order to make unwanted access difficult. Web proxy protection restricts access to Internet sites that are potentially dangerous. The basics of the department's network, such as servers, must also be physically secured from access, preferably with a room that can be locked and is under video surveillance and an alarm. DICOM files should be encrypted with the most secure algorithms available. In response to cyber-attacks, it is necessary to have agreed procedures and such a system must always be on standby. Known attacks on radiological systems are Kwampiris, Petja/NotPetya, Ryuk, Wannacry, Conti group and BianLian.