Starting June 1, the Postal Service™ will begin blocking all unapproved USB mass storage devices on ACE computers.
While the devices are small and may seem harmless, plugging in an unapproved USB device can open a pathway for attackers to access USPS® systems, potentially leading to data leaks or security breaches. This activity also violates USPS policy (see Handbook AS-805 at blue.usps.gov/cpim/ftp/hand/as805/as805c10_006.htm).
USPS personnel who connect an unapproved USB mass storage device, such as a flash drive, external hard drive, or smartphone after this date, may see a pop-up message stating, “Device Blocked by SentinelOne — USB device blocked. Your organization does not allow you to use this device.”
After multiple violations, the matter may be escalated for investigation and further review by USPS security teams. This block does not apply to common peripheral devices such as a mouse, keyboard, or external monitor.
Employees and contractors who need a USPS-approved USB mass storage device for storing and transmitting USPS information can purchase one through the eBuy+ catalog. Any USB device — external hard drive or travel-sized stick — purchased through eBuy+ is USPS-authorized and appropriate for use. Users can browse the selection of devices and narrow their search using the IT Equipment checkbox for the best option based on individual or business needs. Users who do not have access to the catalog may need to contact their manager.
The U.S. Postal Inspection Service (USPIS®) is taking a distinct approach to blocking unauthorized USB devices on the postal network. USPIS ACE users will receive separate communications from the agency with details and specific action steps.
For more information, go to blue.usps.gov/cyber/removable-media.htm or contact the Insider Risk team at insider_risk@usps.gov.
— Corporate Information Security Office,
Chief Information Officer, 5-29-25
