  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 Alexa Top 1 Million
list revealed on 8255 distinct typosquatting URLs a total of 9857 pop-up
messages, out of which 8828 were malicious. The vast majority of those distinct
URLs (7176) 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.
