Sputtering Video

Q:

Every time I want to view a video on YouTube, the video repeatedly starts and stops. Sometimes a five-minute video takes 20 to 30 minutes to view. This happens on all my computers and on my smartphone. What can I do to correct this problem?

A:

Since the problem exists on all your devices, I would guess that it’s an issue of some kind with your network, or perhaps the router or modem you are using. I’m sorry that I can’t precisely diagnose the problem from afar, but I’d suggest talking to your Internet-service provider and troubleshooting the router or modem. Sometimes network issues can be solved by merely rebooting the router, switching it off and then on after a few minutes.

Q:

I have the Fidelity app on my iPhone, and wonder about the security involved in placing stock trades through it.

A:

Remember that a smartphone is really a computer, and nothing in the consumer computer world can be deemed with certainty to be totally secure from the subculture of malicious hackers, whose motives are often financial. Having said that, I am unaware of any incidents in which iPhones in the hands of consumers have been compromised in a way that steals financial data sent over cellular networks. Further, I assume that Fidelity has some form of encryption for such transactions.

Still, I will repeat my oft-stated advice: Never perform confidential online business on any computing device over a public Wi-Fi network.

You can find Mossberg’s Mailbox and Walt’s other columns at http://walt.allthingsd.com. Email mossberg@wsj.com