Skip to content

Comment on I sent my boyfriend a picture of a storm. He got one of a woman and a dogparent

Comments

It’d be MMS since they sent an image. But yes, the sender has an iPhone and the recipient has an Android phone, from looking at the two screenshots. Hence it’s not using iMessage.

MMS is just a SMS with the picture hosted on a proxy server. If you MITM the SMS, you can change the picture URL to another. I am not saying that's what happened; I am saying it could have happened, and rather easily as a prank, too.

MMS is just a SMS with the picture hosted on a proxy server.

Are we sure about that? I don’t know much about the SMS and MMS protocols. And I remember when I had a phone that could only receive SMS, I’d get a link so I could view the message in the browser on a computer, so in that sense it is close to what you are describing. But from my limited understanding of SMS and MMS, I thought MMS is a distinct protocol.

Looking at something that Twilio writes about SMS vs MMS, they say [1]:

MMS […] was built using the same technology as SMS to allow SMS users to send multimedia content.

and then

Standard SMS messages are limited to 160 characters per message. If a message exceeds this limit, it is broken up into multiple segments of 160 characters each, depending on its length. Most carriers today automatically chain these messages together to ensure they arrive in the order they are sent. Unlike SMS, MMS messages do not have a standard limit. While their maximum size depends on the carrier and the device receiving the message, 300 KB is often mentioned as the largest size most carriers will reliably handle.

So MMS sounds like an extension of SMS, but a thing of its own.

I remember with another old phone I had, I’d be asked if I wanted to download the MMS messages I received. But not sure proxy server would be the word for it. To me, from my memory, proxy server seems to apply only when the device is not capable/not configured for receiving MMS.

[1]: https://www.twilio.com/learn/messaging/what-are-sms-and-mms

The MMS content is hosted on a public HTTP server which the ISP themselves host (I'm not entirely sure anymore how the synchronization works). Yes, you may call it a proxy server, but since the data is temporarily cached I call it a proxy server, also the APN settings call it MMS proxy. The definition is pedantic.

Or if you are reusing ids and a glitch happens when the system tries to store the image on the proxy server, the recipient might end up viewing the previous image that happened to use that id. Thankfully nothing embarrassing or incriminating.

AboutSource Built by g1lg1l

Hackerly is an independent reader for Hacker News, built on the public HN API. Not affiliated with Y Combinator.