DNG images contain a checksum (DNG tag is RawImageDigest). When the image is loaded in ACR or Lightroom, we compute the checksum from the image data itself and check the result against the checksum stored in the DNG. Thus we can detect unexpected changes (e.g., file corruption). For example, ACR will warn about a damaged file if there is a checksum mismatch.
We do not yet have a built-in way in Lightroom for the user to run this "verification" procedure in batch mode (i.e., select a bunch of DNGs and run the check).