  Today, many different types of scams can be found on the internet. Online
criminals are always finding new creative ways to trick internet users, be it
in the form of lottery scams, downloading scam apps for smartphones or fake
gambling websites. This paper presents a large-scale study on one particular
delivery method of online scam: pop-up scam on typosquatting domains.
Typosquatting describes the concept of registering domains which are very
similar to existing ones while deliberately containing common typing errors;
these domains are then used to trick online users while under the belief of
browsing the intended website. Pop-up scam uses JavaScript alert boxes to
present a message which attracts the user's attention very effectively, as they
are a blocking user interface element.
  Our study among typosquatting domains derived from the Majestic Million list
utilising an Austrian IP address revealed on 1219 distinct typosquatting URLs a
total of 2577 pop-up messages, out of which 1538 were malicious. Approximately
a third of those distinct URLs (403) were targeted and displayed pop-up
messages to one specific HTTP user agent only. Based on our scans, we present
an in-depth analysis as well as a detailed classification of different
targeting parameters (user agent and language) which triggered varying kinds of
pop-up scams. Furthermore, we expound the differences of current pop-up scam
characteristics in comparison with a previous scan performed in late 2018 and
examine the use of IDN homograph attacks as well as the application of message
localisation using additional scans with IP addresses from the United States
and Japan.
