7.9: Block Unnecessary File Types

Block all email attachments entering the organization’s email gateway if the file types are unnecessary for the organization’s business.

Asset Type

Security Function

Implementation Groups

Network

Protect

2, 3

Dependencies

  • Sub-control 2.5: Integration Software and Hardware Asset Inventories

  • Sub-control 5.1: Establish Secure Configurations

Inputs

  1. The list of endpoints

  2. The organization’s approved email gateway configuration, including file types to be blocked.

Operations

  1. From Input 1, collect endpoints configured as email gateway(s) (M2)

  2. For each endpoint collected in Operation 1, collect the system’s attachment blocking configuration

Measures

  • M1(i) = (For each email gateway “i”) 1 if the email gateway’s configuration complies with the organizations attachment blocking policy; 0 otherwise.

  • M2 = Count of email gateways

Metrics

Coverage

Metric
The ratio of endpoints configured as email gateways that are properly configured to
the total number of email gateway endpoints

Calculation

(SUM from i=1..M2 (M1(i))) / M2