What is screen sharing?
Screen sharing covers a range of tools: the share button in videoconferencing apps such as Microsoft Teams, Zoom, Google Meet and Webex; Quick Assist and the older Windows Remote Assistance (msra.exe) built into Windows; Screen Sharing on macOS; and third-party remote support products such as TeamViewer, AnyDesk and Splashtop. Some sessions are view only. Others let the remote person control the mouse and keyboard. For a help desk, it is the fastest way to see exactly what the user sees, walk them through a fix or do it while they watch.
How the connection works
RDP and VNC usually need a direct network path to the target computer, which means a VPN, open firewall ports or port forwarding when crossing networks. Most remote support and videoconferencing tools work differently. Both the technician's and the user's computers make outbound, encrypted connections, typically HTTPS on TCP port 443, to the vendor's relay service, which joins the two. Because neither side has to accept an inbound connection, no port forwarding is needed, and the tools work from home networks, hotels and coffee shops.
Attended vs unattended access
| Type | How it works | Typical use |
|---|---|---|
| Attended (ad hoc) | The user starts the session by entering a code or accepting a prompt; it ends when either side closes it | Help desk calls, training, quick fixes |
| Unattended | An agent stays installed, and technicians connect with their own credentials without the user present | Servers, kiosks, after-hours maintenance; overlaps with RMM tools |
| View only | The remote person can watch but not click or type | Demonstrations, reviewing a problem |
Quick Assist in brief
Quick Assist is included with Windows 10 and Windows 11. The helper signs in with a Microsoft account and receives a short-lived security code. The person being helped enters the code, sees who is trying to connect and decides whether to allow it. The helper can request full control or view only, and either side can end the session. Windows Remote Assistance is the older built-in option and uses invitation files.
Security considerations
- Verify identity both ways: confirm the user and the ticket, and give the user a way to confirm you, such as a ticket number or a known callback number.
- Get consent: explain what you will do, ask the user to close documents with sensitive data and use view only when you do not need control.
- End sessions cleanly: disconnect when finished, confirm the session closed and remove one-time agents if policy requires.
- Protect unattended access: use approved tools only, MFA on technician accounts, logging and, where policy calls for it, session recording. Stolen technician credentials can open every managed machine.
- Keep tools patched: remote support software is a frequent attack target.
- Watch for unsolicited support scams: criminals phone people or show fake virus pop-ups, then talk victims into installing a legitimate screen-sharing tool so they can take over, install malware or reach bank accounts. Real IT departments and major vendors do not cold-call users to fix their computers.
Screen sharing vs RDP and VNC
RDP (TCP 3389) normally opens a separate session and locks the local console, so the user does not see what the technician does. VNC (TCP 5900) shares the live desktop across operating systems but is not encrypted by default in many implementations. Screen-sharing tools share the live desktop like VNC, get through firewalls by way of a relay and depend on a vendor service and its licensing.
Screen sharing on the CompTIA A+ exam
Core 2 (220-1202) objective 4.9 covers remote access technologies and the security considerations for each. If a scenario involves a home user behind a router you do not manage, and the user should watch the fix, think screen-sharing tool or Quick Assist. If someone calls a user out of the blue and asks them to install remote access software, think tech support scam. If a question asks how to secure remote support, think user consent, identity verification, MFA for technician accounts and closing sessions when finished.