74 MACWORLD OCTOBER 2019
iOSCENTRAL REVIEW: FIREWALL: ROBO CALL BLOCKERsomeone you know using a different
number, they can be added to the whitelist
in a couple taps.A FEW CAVEATS
Remarkable as Firewall is snuffing out
solicitors, there are a few limitations worth
noting. For starters, the app currently only
works in the U.S. with AT&T, Sprint,
T-Mobile, and Verizon. Intercepted calls
are redirected to your iPhone using VoIP,
which consumes cellular or Wi-Fi data
rather than plan minutes.called Firewall (go.macworld.com/
frwl) takes the opposite approach:
Whitelisting everyone you know
and sending the rest to limbo.
While that may sound like
dropping a nuke on your
backyard to get rid of a few
pesky bugs, Firewall did a
remarkable job of eliminating
nuisance calls on my iPhone X.
In recent months I’ve received
a handful of daily intrusions, but
after installing Firewall, they
were entirely eliminated.
The app accomplishes this
feat by forwarding incoming
cellular (but not FaceTime) calls
to the company’s servers, where
unknown numbers are vetted
against multiple known spam
databases. Anything that
survives this first line of defense is then
matched against a whitelist of your device
contacts, with everyone else going to
built-in voicemail.
When active, Firewall emulates the
look and feel of a traditional iPhone in-call
experience. The app bypasses carrier-
based voicemail, transcribing recorded
audio with a far higher degree of accuracy
than iOS or Google Voice—so good in fact,
that you can understand every voicemail
just by reading, rather than listening.
Should a blocked caller turn out to be
Firewall mimics the iPhone in-call experience, with an
option to reroute VoIP calls to your cellular carrier at
the tap of a button.