In true caller-ID spirit, today the app Truecaller blocks between 38 billion and 40 billion spam calls annually for its 374 million+ users. Now, in hopes of getting more people to sign on to its premium tiers, it's turning up the dials on its filtering technology. The new "Max" version of the Android premium subscription uses AI to automatically block every call that does not come from an approved contact, or which its AI determines might be spam, even if not already listed in Truecaller's database. Previously, what got blocked and other treatments were governed by listings on that database, combined with the individual's proactive screening.

The update is Android only: Apple doesn't allow Truecaller-and indeed any other caller ID service to check the status of callers as spammers to automatically block calls on iOS. As such, Truecaller has a far more stripped-back service for iPhone users based around CallKit.

The moves come at a critical business juncture for the company. In Q4, Truecaller saw a 4% year-on-year revenue dip on $41.52 million in sales. In India — Truecaller's biggest market, with 259 million users — the Indian telecom regulator recently proposed a Truecaller-like caller ID service, to be implemented across all telecom networks in the country, as a bid to better fight spam. So far, that proposal has seen resistance on grounds of privacy and technology; if put in place, though, it would pose a direct competitive threat to Truecaller.

It speaks to how Truecaller believes there could be a business opportunity banking on people fed up with spammers' insidious ways — even if a fix could come at the cost of missing calls from unknown numbers and non-spammers that might actually be welcomed.

Another is that current interest in everything AI: Truecaller's two core features are caller ID and spam protection. It hopes that the reservations about AI might be outweighed by curiosity over how well it might work to do Truecaller's main job. while also growing its premium sign-ups at the same time.

The pricing for premium tiers ranges from $9.99/month to $99.99/year, and also depends upon the factors shown above, in terms of number of users covered .

This new feature is also a signal in regards to how Truecaller is playing around with ways to bring in more proactive automation—and subsequently expect less proactive engagement from its users themselves. Truecaller has always provided subscribers with a list of all the calls it might block, including international, hidden, and unknown numbers not found in someone's contacts. Still, to get the most out of the app, users have had to activate and tweak the lists on their own. Now, everything flagged as suspicious will be blocked by default.

"It's something that at least some people have asked for—people who understand the app very well," said Kunal Dua, vice president of search at Truecaller, over the phone.

That is not the first AI feature at Truecaller: It offers an AI assistant that scans calls to figure out why the caller has dialed the user. Other non-AI features include cloud telephony and call recording.

The AI behind Max has been in development for some time now. According to Dua, the firm has been testing "multiple dozen algorithms" across its markets to identify spam numbers, and each of these machine learning algorithms is also learning from the user feedback.

But it would really be a sea-change at Apple to bring the service to the millions of iOS users. Last year Truecaller added live caller ID support to iOS, though that is even more limited and, with iPhone users having to go through a process for setting up live caller ID.

How users will react to the all-in nature of the feature, which sometimes will err, only time will tell. The app today already warns the users that the feature "may misclassify legitimate businesses." But Dua says the system should continually improve over time as it gets more data on spam calls.

"That's not to say we don't try to differentiate between spam and legitimate businesses," he says. "But there may be particular cases where some legitimate businesses may be short-term [blocked], he said. "We like to believe that it's short-term in front of our community and before our AI algorithms can flag that this is actually a legitimate business. … We have a great amount of confidence that if we are calling somebody as a spammer, there is a very, very high probability, 99.999 times out of 100."

The user can unblock a number, for instance, if marked as spam by its algorithms, which also has the effect of training the AI.

Users can access the new spam-blocking feature by updating their Truecaller app to 13.58 or later and then clicking on Settings > Block.