/usr/share/vim/vim73/syntax/dns.vim is in vim-runtime 2:7.3.429-2ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | " Vim syntax file
" Language: DNS/BIND Zone File
" This has been replaced by the bindzone syntax
:runtime! syntax/bindzone.vim
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