As an option, you can encrypt data files with PGP encryption when sending them to Audience Manager.
Download the Audience Manager public key (https://marketing.adobe.com/resources/help/en_US/aam/downloads/adobe_pgp.pub).
Import the public key to your trusted store.
For example, if you use GPG, the command could be similar to the following:
gpg --import adobe_pgp.pub
You should see a message similar to the following:
pub 4096R/8496CE32 2013-11-01 uid Adobe AudienceManager sub 4096R/E3F2A363 2013-11-01
Encrypt the inbound data using the following command:
gpg --recipient "Adobe AudienceManager" --cipher-algo AES --output $output.gpg --encrypt $inbound
All encrypted data must use .pgp or .gpg as the file extension (e.g. ftp_dpm_100_123456789.sync.pgp or ftp_dpm_100_123456789.overwrite.gpg).