Manufacturing systems' digital transformations increase the vulnerability of industrial systems. Cyber security is a continuous cat-and-mouse game. Vulnerabilities are found and fixed, but hackers are usually one step ahead. Cyber security resonates at all levels of society, and the Internet of Things is bringing new threats in this area. Security investments increase while technology development proceeds. Transformation in technology, globalization, and business models that prefer networking and subcontracting set new cyber-security requirements for SMEs. In this paper, we review the security challenges of SME manufacturing companies and suggest cyber-security management solutions for SMEs.