Here’s why MTN actually capped free Twitter: a loophole that landed some customers R18,000 worth of free data per day

Business Insider SA
  • MTN this week announced a cap on free Twitter use on its network because "the free Twitter IP is being hacked".
  • But neither the MTN nor Twitter networks were compromised, the cellphone company says.
  • Instead, some "sophisticated" users exploited a loophole – to get up to R18,000 worth of data free per day.

MTN has put a cap on free Twitter use for all its customers not because its systems were hacked, but as an additional way to combat "some very smart guys" who had found a loophole, the company's general manager of network planning Zoltan Miklos says.

Its systems were never compromised, the company now says – even though it seemed to suggest just that earlier in the week.

In an announcement on Monday, MTN said "it’s clear that the free Twitter IP is being hacked to stream IPs that are not free", referring to internet protocol (IP) addresses, the system used to route traffic to internet servers.

The ability to confuse MTN's network about which IP address is which would suggest a sophisticated attack, with implications for the security of services such as online banking.

On Wednesday MTN said it stands by that statement, though it described what amounts to a technical loophole rather than hacking in response to questions from Business Insider South Africa.

There were "some sophisticated guys who understand just how these networks work", says Miklos, and the new data cap is a way to stay ahead of them.

Twitter publishes a range of IP addresses used by its service, and MTN does not bill for data to those IP addresses, as long as the data is in the formats Twitter uses.

But Twitter shares contend-delivery networks (CDNs), systems used to quickly stream heavy content such as video, with other companies. By formatting data to look like Twitter traffic, a small handful of users were able to download files or stream video from those CDNs without paying.

MTN would not provide detailed numbers on the abuse it had recorded, but said it had identified a group of around 100 people who were regularly using 600GB of data a day to supposedly access Twitter.

That equates to each of those users downloading around a dozen high-definition movies every day – and to around R18,000 worth of data per day, at MTN's standard rates.

"This is the kind of excessive traffic we are seeking to limit," said MTN spokesperson Jacqui O'Sullivan.

As a result, it has instituted a 500MB per day cap for Twitter use. The vast majority of its millions of customers need about a hundredth of that amount, according to MTN's analysis. Heavy users, who access a lot of live video streaming from other Twitter users, could conceivably used 50MB to 100MB per days, says Miklos, but reaching 500MB should be near impossible – for actual Twitter use.

MTN uses a range of defences against unfair use of its network, Miklos says, including heuristic inspection that spots unusual traffic patterns. But staying ahead of those looking for loopholes can be tough, and a data cap provides a "simple guardrail".

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