FIPS = Federal Information Processing Standard

FIPS 140-2 defines four levels of security:
Level 1 > Basic security requirements are specified for a cryptographic module (eg. at least one Approved algorithm or Approved security function shall be used).
Level 2 > Also has features that show evidence of tampering.
Level 3 > Also prevents the intruder from gaining access to critical security parameters (CSPs) held within the cryptographic module.
Level 4 > Provides a complete envelope of protection around the cryptographic module with the intent of detecting and responding to all unauthorized attempts at physical access.