New security-through-obscurity tactic: make sure to automatically send lots of fake emails between employees, containing importantly-sounding words such as "classified", "secret" and "important" — with some identifying characteristic that makes the employees' email clients ignore them.
Then an email dump of 45 GB of useful information could instead be 4.5 TB (with 1% useful information), and wading through all the non-information to find something useful will not be worth the time of the adversary. The more important information you have in emails the more you need to increase the misinformation-to-information ratio.
Then an email dump of 45 GB of useful information could instead be 4.5 TB (with 1% useful information), and wading through all the non-information to find something useful will not be worth the time of the adversary. The more important information you have in emails the more you need to increase the misinformation-to-information ratio.