Yes, you can check the SHA1
or MD5
checksum.
You didn't specify which ROM you are downloading. Let's have a look at the Nexus stock ROMs:
https://developers.google.com/android/nexus/images#mantaray
There is a download link and a version number and checksums listed like that:
- Version: 4.2.2 (JDQ39)
- Link: https://dl.google.com/dl/android/aosp/mantaray-jdq39-factory-d79f489e.tgz
- MD5:
b7a1162fb4e617143306ef6c4ca6c040
- SHA1:
d79f489e1001d183b31d8a407b47cd5b8e9505cd
To verify a checksum you can do it via command line:
$ md5sum mantaray-jdq39-factory-d79f489e.tgz
b7a1162fb4e617143306ef6c4ca6c040
Or:
$ openssl sha1 mantaray-jdq39-factory-d79f489e.tgz
SHA1(mantaray-jdq39-factory-d79f489e.tgz)= d79f489e1001d183b31d8a407b47cd5b8e9505cd
If it matches with the one stated at the google page, you can assume the file is not corrupted or modified.
Note: Linux, MacOS, Windows
The terminal commands only work out of the box in MacOS or Linux. To verify checksums in Windows there is a tool by Microsoft called Checksum Integrity VerifierChecksum Integrity Verifier: http://www.microsoft.com/en-us/download/details.aspx?id=11533.