Finding marathon cheats using Amazon Rekognition

In the last few weeks many articles have been published about the problem of cheating  in the biggest running events, for example Beijing marathon to use facial recognition in cheating crackdown.

There is apparently even a former marathoner and business analyst, Derek Murphy, who devotes his time to catch the cheats, as the BBC recently reported : The man who catches marathon cheats – from his home. The booming of the biggest international marathons, the grow of qualifying events for the most prestigious ones make the likelihood of cheating higher, with bib-swappers who give their chips to a faster runner and bib-mules who carry more than one chip during the entire race.

Is it really cheating?

Let me start saying that I am not a big fan of blaming “marathon cheats” in public forums. There are  scenarios when a runner might decide to take part in a race using the number of someone else and most of the them do not hurt the community or other runners. Qualifying for the UTMB or for Boston Marathon at the expenses of other runners is of course not one of them. There are a few hundred trail events that allow runners to collect points for the UTMB, even more road marathons that can give you an official time good enough to go to Boston. You can find most of them on RaceBase World.

Screenshot from 2017-04-26 17-08-52

I have been running almost 100 races in different countries in the last 15 years, I have a volunteered in a dozen of running events in Berlin alone and I do not need face recognition to figure out that there are indeed a few runners every race who are running with someone else number. And I never did anything to stop them.

Data privacy and marathon running

Before testing Amazon Rekognition as a tool to find cheats in marathons, we might want to discuss if facial recognition technology is really a threat to privacy and how we can have data without contacting the race organizer.

Unfortunately runners have been used for some times. While you might take good care of your data on-line, make sure not to post to social networks or remove geolocation information from your pictures, there is nothing you can really do if you are a runner to avoid your personal data being shared everywhere.

You run 42 kilometers with a number on your shirt and everyone can find all the pictures for a given runner and his personal data (often including date of birth and residence) on public websites. Last year I was able to figure out personal information about the girlfriend of a old schoolmate I have not met in 20 years simply by looking at the pictures and results of a old Berlin Marathon only.

Is face recognition during a marathon actually possible?

Using facial recognition to address cheating crackdown in a recreational event feels like using a machete to cut the salad but does it actually deliver?  Can Amazon Rekognition help in validating the results of qualifying races for UTMB or Boston?

As a first test, I took the images of the latest marathon I run (OK, I barely finished walking), the Berlin Marathon 2016. And I of course compared the very first picture in the set associated with my number (the one before the start) with the last one, after crossing the finish line.


Amazon Rekognition simply confirms something that runners have always known, a marathon changes you. After completing a 42K you are not the same person anymore.

Jokes aside, this is just a one picture test on one runner but highlights the challenges of tracking the runner along the race using face recognition alone. It might help combined with other technologies but it is likely to generate a significant number of false positives.

Testing a few more pictures from my previous races still available on-line (the not existent data privacy for runners), I had mixed results. Some pictures match easily others do not. Some are false positives others are not. And I was definitely younger.

Screenshot from 2017-04-24 21-06-43
A random test with the London Marathon

Let’s instead limit the goal to confirm that a runner taking part in an event matches by gender and age with the category she was registered for. That’s the most common scenario of cheating that is impossible to cover using split times along the course.

Think about your younger and fitter cousin making your PB so you can qualify for the Boston Marathon, your long term running pal who collects a few points for you so you can qualify for the UTMB next year.

Last Sunday took place the London Marathon, the largest spring marathon in Europe and one of the biggest in the world with New York, Berlin and Paris.

All the results  of the race are of course available online, and there is a simple GET request that returns the data for a given bib number*****&search%5Bsex%5D=%25&search%5Bnation%5D=%25&search_sort=name

In the same way you can access all the pictures of all the runners on MarathonPhoto and retrieve the pictures of a runner using again the start number and the last name you got from the previous request (the RaceOID is the one of the London Marathon 2017).****&BibNumber=*****

We do not want (yet) to process 30K or 40K runners, let’s use a very small sample to see how Amazon Rekognition works. Let’s use to get 10 numbers we can test.


Three of them did not match any runner (not all numbers are assigned for the race) and one runner did not start at the event. What about the other 6 runners? We know the category (age range) and the gender for all of them.

- 31724 (18-39, male) 
- 10297 (18-39, male)
- 12471 (18-39, male) 
- 19412 (18-39, female) 
- 17970 (45-49, female) 
- 21095 (18-39, female)

Retrieving the first image of the set of each one using the MarathonFoto URL, we are able to double check the runners using Amazon Rekognition to match the above data with the results with face recognition.

How did Amazon Rekognition score?

- 31724 (35-52, male 99,9%)
- 10297 (29-45, male 99.9%)
- 12471 (14-23, male 99.9%)
- 19412 (23-38, female 100%)
- 17970 (20-38, female 100%)
- 21095 (30-47, female 100%)

It did very well. All runners matched the expected gender.

Even if there was a bit of luck as in one of the picture Amazon Rekognition selected a different and incorrect runner in the corner of the photo. And this will be the biggest  challenge for an automatic bot: we need to first match the bib number in the image with the race number as there might be multiple runners in the same shot, so combine the technology already used to map the bib number to the photo to face recognition.

Did all runners match the expected age range as well? In short, yes.

The only failure (12471) is due to picking up the wrong face in the picture, but once address that is correct too.  Note as well that for runner 12471 the overlapping of the age range is minimum. But even when the overlapping is minimum, the correct age is in the range (you can find that information searching the athlete name on-line: 31724 is 39 and 21095 is 33).


So we have a few limitations here that working with a race organizer can easily address:

  1. The London Marathon is sensible enough to publish the age category but not the year or date of birth. A data of course they have. And that (wrongly) many race organizers make public.
  2.  The pictures are screenshots from the MarathonFoto site and are not the best quality (I did not pay for them).
  3. We need to parse multiple photo of each runner to have a significant confidence and that might increase the cost of the solution


Of course a very small set of a few runners is not expect to catch cheaters (and I would not publish their data anyway) but confirms that the approach of face recognition to catch cheats in marathons is feasible even if it most likely needs other tools too to have a reasonable level of accuracy.

But running a full data validation for a big event requires just the collaboration of the race organizer, a few dollars, maybe an instance running Scrapy and a couple of AWS Lambda function. But everyone today can create profiles of thousands of marathon runners around the world and verify their data. Whatever that is good or not.

But I still believe that at the moment the claim of the Beijing Marathon is more a PR stunt than the real way they are going to use to address the issue.