Joe walks up to a security guard with an unknown person and states a phrase. After they leave, the security guard calls the policeas the security guard believes Joeis in trouble. The phrase Joe stated is an example of a:

Procedure
Duress code
Separation procedure
Access attempt

Duress code

Explanation:

A duress code is a way of letting a central station operator know that help is needed immediately. Verbal duress code Is a spoken passphrase that is provided to the security people when one is in danger as Joe did to the security man.

Duress Code

Explanation:

A duress code is used by an individual to make a signal when he is being kept hostage by an assailant by using it to signal others that they are in trouble.

Duress codes can also means secret passwords that allow a person to request for emergency help by entering the code when under duress from an assailant in order to trigger a silent alarm by alerting police or security personnel.

Therefore DURESS CODE was what Joe use when he walks up to a security guard with an unknown person and states a phrase. Making the security guard to call the police as the security guard believes Joe was in trouble.