Ransomware, which makes devices unusable until their owners pay to unlock them, has become increasingly prevalent in the past year, they say.
Devices holding photos, emails and fitness information could be targeted.
The risk to business is "significant and growing", the National Crime Agency and National Cyber Security Centre say.
The joint report from the NCA and the NCSC says cyber crime is becoming more aggressive.
More devices connecting to the internet meant opportunities for criminals, the report said.