According to the dhs agent portrayed in this video, the secret service has responded to network intrusions at businesses throughout the united states that have been impacted by through their point-of-sale systems.

malware

Explanation:

The answer is "malware".

The secret service agent carefully analysed and suspected that the intruders have have infected the internet network system by a harmful malware that impacted the entire network system in the United States at the point-of-sale systems.

The malware is a virus which hackers and cyber criminals used to steal data and information or mislead people or government.

Thus the answer is "malware".

i go with [ a