S 5.28 Acknowledging correct fax origin via telephone

Initiation responsibility: Supervisor, IT Security Officer

Implementation responsibility: User

In the event of important or unusual fax transmissions, checking with the sender of the fax that he/she sent the fax and that the fax was not falsified by a third party should be taken into consideration. This may easily be performed by calling the sender on the telephone. The required telephone number is generally documented on the fax cover sheet, but should be verified, since it could have been falsified.

Review questions:

• Is the callback function of a modem only enabled on the passive side of data transmission (used to retrieve files or files are installed on)?
• Are the preset callback telephone numbers checked and updated regularly for modems?
• Have the recipients of important or unusual fax transmissions been instructed to check with the sender of the fax that the contents are correct ?