TP-Link TL-R470T Plus Configuration Manual page 120

Configuring Behavior Control
File Suffix
Effective
Description
Status
2) In the General section, enable Web Security and click Save:
Enter file suffixes to specify the file types. Use Enter key, Space key, "," or ";"
to divide different file suffixes. The hosts of the selected IP group cannot
download these types of files from the internet.
Select the effective time. The effective time referenced here can be
created on the Preferences > Time Range page.
Enter a brief description for the group.
Check the box to enable the rule.
Behavior Control Configuration
Configuration Guide 113