A recent post on reddit provided some details of current fraud protection capabilities of banks. In this case Barcely used a font installed by TeamViewer to flag a transaction.
TeamViewer is using this font when starting a session via their website. JavaScript will try to detect the font, which would indicate whether TeamViewer is installed. More background information is available here and here. Günter Born pointed out that common font-fingerprinting libraries on GitHub already check for TeamViewer13, TeamViewer14 and TeamViewer15, so any website can run the same test. TeamViewer also provided some details:
The TeamViewer font is used to implement a smooth user experience from web to the native client