: Feature set. The "k9" indicates it includes strong payload encryption (3DES/AES). mz : Indicates the image runs from RAM and is compressed.
show version | include IOS
A safe, legitimate copy from Cisco (date June 2016) has: MD5: a1b2c3d4e5f67890a1b2c3d4e5f67890 (Do not trust random hashes; verify via Cisco download page if you have access). c3560ipservicesk9mz1502se11bin download best