Blacklisted apps are those that figure on at least one blacklist, such as VirusTotal, a Google-owned site; files can be uploaded to this site and they are scanned by more than 70 anti-virus engines to indicate whether they are kosher or not.
The report said the percentage of blacklisted apps relative to total number of apps monitored by it grew for the second consecutive quarter, going from 1.95% to 2.1%.
The blacklisted apps carried out actions such as brand imitation, phishing and hosting malware. Apart from this, there were many apps dedicated to deceiving users with bogus messages about tax returns.
RiskIQ said app downloads would reach 260 billion by 2022; it had observed 2,554,616 mobile apps in the second quarter of 2019, a rise of nearly 11% over the first quarter.
The number of apps in the Google Play Store grew by 164,101 in quarter two, 38% less than in the first quarter and 189% less than in the third quarter of 2018. Apple increased its app inventory by 14.3% or 116,210. Of the 106 billion downloads from these two stores, 76 billion were Android apps.
Google always allows some blacklisted apps into its store, but RiskIQ said the company had been increasing its emphasis on safety. Three apps stores — 9Game.com, Zhushou and Vmallapps — were the worst offenders when it came to hosting blacklisted apps, with 95% of the total apps available from 9Game.com being blacklisted.
"As usual, feral apps, or apps not in any store and downloaded directly from the Internet, proved to be exceptionally dangerous, with a 51% blacklist rate," the report said. "Quarter after quarter, the data confirms that apps downloaded outside of the Google Play store and the Apple App Store are riskiest."