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Block SMS Text Spam with Nomorobo

Have you been getting more SMS spam? If not, count yourself lucky, because my SMS spam load has gone through the roof recently. Apple’s built-in option to filter unknown senders did what it promised but forced me to sort through all the texts from unknown senders for legitimate messages. I tried several SMS spam filters, none of which caught much of anything. Eventually, I settled on the longstanding call-protection service Nomorobo, which reined in the problem.

Nomorobo splash screen

Spam Keeps Evolving

Years ago, email spam was a huge problem. There was an escalating war between spammers and spam filters. Eventually, spam filter technology won. Although email spam is still a thing, the vast majority of it is automatically filtered away. The main reason I use Gmail is its exemplary spam filtering. Those whose email provider isn’t as good as Gmail can eliminate most spam with C-Command Software’s venerable SpamSieve.

Then phone spam appeared. I received so many calls from telemarketers trying to sell me car warranties that I stopped answering calls from numbers I didn’t recognize. Just as it seemed hopeless, Apple added the Silence Unknown Callers option (Settings > Phone > Silence Unknown Callers). Now calls from anyone not in my Contacts go straight to voicemail. Most spammers no longer leave voicemail; presumably, it’s ineffective for whatever scam they’re running. When a real person leaves me a voicemail, like my dentist confirming an appointment, I add that number to Contacts so they ring through the next time.

Silence Unknown Callers

The latest spam frontier is SMS text spam. I used to receive a few spam texts, but now I may get a dozen a day. I get texts that an Amazon package I never ordered can’t be delivered unless I click “” and sign in with my Amazon password. I get texts from “Jenny” asking, “Do you want some fun tonight?” But mostly I get texts from politicians asking for money. Somehow I’ve ended up on the lists for both US political parties. As the US election season heats up, the political spam is only getting worse.

Simple Solutions That Didn’t Work

First, I figured I’d try Apple’s built-in filtering. I turned on Settings > Messages > Filter Unknown Senders. That gives Messages a Filters link at the top left of the screen; tapping it reveals a list of filters that separate messages into Known Senders and Unknown Senders. Texts from numbers not in my Contacts appear in Unknown Senders, which sounds positive but proves relatively ineffective. The problem is that I still have to look through the Unknown Senders list for DoorDash orders, Uber confirmations, and two-factor authentication codes from numerous sites. Worse, some political spam texts appeared in Known Senders even though I don’t have contacts for them.

Filter Unknown Senders and effect on Messages

Next, I tried blocking the phone numbers from which the spam texts originate. But each message comes from a unique number, presumably spoofed in many cases, which is easy to do. (I never tried replying to the actual scams.) I quickly accumulated hundreds of blocked numbers on my iPhone, but there was no reduction in spam texts.

For a while, I was religious about deleting spam texts and tapping Delete and Report Junk, but that doesn’t seem to do anything. After months of reporting junk, I didn’t notice any reduction in spam. I gather that reporting SMS text messages like this sends them to your carrier (you can also forward the messages to 7726), which can use the information to block similar spam texts. If the carriers actually do this, it’s ineffective. With messages sent via iMessage, reporting them sends the information to Apple. I don’t know anyone in the appropriate group at Apple, but other contacts in the company say they believe Apple uses the reports to help detect and revoke spammer accounts with enough reports.

Block caller and Report Junk texts

Some texts claim you can opt out by replying STOP, but I was reluctant to try this in many cases because it would confirm to a scammer that my number was live, possibly leading to even more text spam. Replying with STOP does work with political spam, but only with that particular candidate, so fighting political text spam becomes a game of Whac-A-Mole. Silence one candidate, and another pops up. (They’re not even local!)

SMS Spam Filtering Apps

Surely there’s an app for that. Next, I decided to try text spam filters. There are a bunch in the App Store that use Apple’s official SMS and MMS Message Filtering API. Most of these filter apps require a subscription.

You install all these products similarly because they use Apple’s API. Once you’ve downloaded one of these apps, go to Settings > Messages > Unknown & Spam, turn on Filter Unknown Senders, and select your SMS filtering app.

Enabling Nomorobo

When you install a filtering app, the list of filters in Messages on your iPhone expands to include Transactions, Promotions, and Junk. If you have an iPad, Messages shows the same categories, and the messages are synced to them via iCloud Messages, which can sometimes stall for a few hours. The macOS version of Messages displays only the Known Senders and Unknown Senders lists in its View menu; messages filtered to the other groups are unavailable.

Nomorobo changes to Messages on iPhone but not on Mac

My testing was rather unscientific since I was primarily interested in solving my immediate problem. I used each spam filter on my own iPhone. Yes, that’s a sample size of one, but they were all working in the same environment. Nor did I try every SMS filter in the App Store. Finally, most of these products block spam voice calls as well as spam texts, but I only tested the spam text feature—Silence Unknown Callers works well enough for me.

I don’t mind paying for an SMS spam filtering app, but cost was still a factor. The winning app also had to work automatically and not make unnecessary requests for data, both of which turned out to be issues. Here are the apps I tried:

  • AT&T Active Armor: Each of the major US cellular carriers (AT&T, T-Mobile, and Verizon) has a free spam filter in the App Store. AT&T’s app is called AT&T Active Armor, Verizon has Verizon Call Shield iPhone, and T-Mobile offers T-Mobile Scam Shield. Verizon’s and T-Mobile’s apps only catch spam voice calls, not texts. Since I use AT&T, I tested AT&T Active Armor. It caught only 5% of my spam texts.
  • Nomorobo: Telephone Science Corporation, the company behind Nomorobo, is a decade old. Originally, the Nomorobo service blocked spam calls to landlines before expanding to protect cellular numbers from calls and then texts. After a 14-day free trial, Nomorobo costs $1.99 per month or $19.99 per year. The Nomorobo app identified 82% of my spam texts, placing them in the Junk list in Messages. That was far better than any of the other apps. It had no false positives—good texts identified as spam—but neither did the other apps.
  • Robokiller: The Robokiller app offers a 7-day free trial, after which it costs between $4.99 and $7.99 per week or $39.99 to $149.99 per year, depending on which plan you buy. Robokiller would not activate without full access to my contacts, which I refused to give. There didn’t seem to be any way around this, so I didn’t go further with Robokiller.
  • SMS Spam Block: Although the SMS Spam Block app is free, it is also fully manual and hasn’t been updated in six years. You must set up a block list of disallowed words that filter out a message and an allow list that lets a message pass. I didn’t test SMS Spam Block because I was looking for an automated solution.
  • TextKiller: A separate app by the company behind RoboKiller, TextKiller also claims to block 99% of unwanted text messages. After a 7-day free trial, it costs $5.99 per month or $79.99 per year (which seems too high), between Nomorobo and Robokiller. The first time I tried TextKiller, the installation failed with an error message that seemed to indicate the company’s server was down. When I tried again a few days later, it installed successfully. During testing, TetxtKiller turned off the setting to filter texts for no obvious reason, so I turned it back on. TextKiller filtered only 6% of my spam texts.

You can see why I stopped when I found Nomorobo, which was the cheapest and most effective of the commercial apps. AT&T Active Armor is free but ineffective. SMS Spam Block is also free but would have required me to maintain lists manually and hasn’t been updated in six years. Robokiller triggered my alarm bells by refusing to activate without access to my contacts and was extremely expensive. TextKiller didn’t instill confidence with its installation error and caught almost none of my spam.

If other text spam filtering apps have worked well for you, please share the details in the comments. But I’ll be subscribing to Nomorobo. $20 per year is a small price to pay for eliminating a dozen text message interruptions per day.


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Comments About Block SMS Text Spam with Nomorobo

Notable Replies

  1. @das
    I have the MalwareBytes which can also perform some filtering. Did you look at it or did it not come up on your radar.

    I’m curious how it performs. I just restored my subscription and turned on SMS filtering. I’ll post an update after a few days. I have been receiving between 2 and 6 political spam texts each day, so I should know pretty quickly how well the filtering is performing.

  2. Jonathan I didn’t know MalwareBytes could do SMS spam filtering, I’ll have to check it out and see how well it works. Their Mac malware scan is very good. As I mentioned in the article, this wasn’t a comprehensive look at every SMS spam filter in the app store.

    One thing I noticed installing MalwareBytes is that the app forces you to buy one of the yearly subscription options. There is also a monthly subscription, which you can switch to later in Settings > Subscriptions, but the app doesn’t tell you that, or let you select it.

  3. Is there the equivalent of Nomorobo in Australia?
    Frankly this whole spam issue is mostly the fault of slack/greedy telephone service providers. It is deplorable that the system allows nuisance callers to spoof valid phone numbers.
    The same for robocalls - how difficult is it to identify them? At the very least subscribers (victims) should be able to opt out of them.

  4. So far MalwareBytes spam filtering isn’t doing well. I’ve had it installed on my iPhone all day. I’ve received 8 spam texts so far, MalwareBytes caught none of them.

  5. All of your frustrations rang true to me as well, I have been getting so many messages from political beggars asking for donations, I could scream. They always start off calling me Kathryn. I am not Kathryn.

    I was in the process of setting up Nomorobo, when I checked on the price after the free period. Seems I downloaded Nomorobo Max somehow. It has a yearly price of $79.99 single or $99.99 family.

    I’m wondering now how effective Nomorobo will be compared to their premium product.

    Did you happen upon Nomorobo Max during your research?

    I’m going to hold off doing the sign up until I get more information. If anyone has compared Nomorobo and the Max editions, please share your results here.

  6. It is not $20 per year it is $60 per year

  7. I am guessing we are all at a loss why you cannot block all calls & messages that are not in your contacts. I am guessing this has something to do with 2FA.

    I keep on adding the scammer/spammer to the Apple blocked list and never respond to any of them.

    The only other issue I have: Is not being able to set MacOS to “Known Sender Only” ( As the default )

  8. I tried NoMoRobo a couple of years ago. It worked great for spam calls but I never enabled the spam text blocking because I didn’t love the idea of letting them read all of my texts.

    The app says:

    “When you receive an SMS message, your iPhone will send the sender’s phone number and the contents of that SMS message to Nomorobo. This allows Nomorobo to analyze the contents of text messages and proactively block new spammers based on message content rather than simply blocking messages from a list of phone numbers. As time goes on, the Spam Text Blocker will get better and better. “

    Anyone else have an issue with that?

    $4.99 a month per phone is my charge

  10. Check your plan. Some include it, while others don’t but you can add it as an extra charge. If your plan says it is included, then contact Billing and ask them to remove the $4.99 charge. They won’t refund prior charges though, I asked.

    EDIT: I found this in an AT&T support article ( Get The AT&T ActiveArmor Mobile Security App - AT&T Wireless Customer Support ):
    “AT&T ActiveArmorSM mobile security is free with your AT&T Wireless® or AT&T Prepaid® service.”
    “Advanced mobile security is included at no extra charge with our AT&T Unlimited Premium®, Unlimited ExtraSM, and Unlimited Elite® (no longer sold) wireless plans. Don’t have one of these plans? You can purchase advanced mobile security for $3.99 per month.”

  11. Has Nomorobo dropped landline? I’m told it is only for wireless and VOIP lines.

  12. @coopermj I tested the cheapest plan from Nomorobo which is $20/year. They do have more expansive plans which add other features, but I think the SMS spam filtering is the same.

  13. GV

    As I usually do, I went to the App Store to peruse Nomorobo reviews before I decide to download an app. . . I start with the “most recent” comments, since the info tends to be more relevant i.e. things can get better or worse over-time.

    Based on the number of negative reviews, I am going to pass. . . I didn’t even bother to check the “most critical” reviews since there would be so many duplicates from the “most recent” category.

  14. @das My experience is mirroring yours. I re-enabled the text filtering in MalwareBytes and it picked up none.
    I installed and enabled Nomorobo and it has flagged all the spams that have arrived.
    Now if my Mac would just recognize the categorizations that Nomorobo has done so I don’t have to see them there…

  15. This is my issue as well. First, as noted above, an item marked by Nomorobo as “junk” on the iPhone remains on the Mac like every other text message.

    Second (and this is bizarre), if I delete a Nomorobo-designated junk message from the iPhone, the same message remains on the Mac for several hours. Eventually the deleted message disappears from the Mac, but I have noticed that the delay can run 12+ hours.

    Perhaps Nomorobo is temporarily hiding the message before permanently deleting it, or perhaps Nomorobo is somehow creating a delay in the syncing of deleted messages between iPhone and Mac.

  16. I have the distinct feeling that the kind of spam messages I’m trying to block won’t be blocked by any service, which is a shame.

    Mine start with a very innocuous greeting like “hi, how are you?”, but invariably if you answer them, you’ll be on the text with them for hours. I did that twice, but never again.

    I can’t shut off unknown callers or texters, because a new customer might call or text me.

    Nomorobo is however, less than half the cost of Verizon Call Filter Plus.

  17. That’s good. I get those but I never answer a text from somebody I don’t know. (Just once I had someone follow up when I didn’t respond - it was a sales person from a home solar installation company.) I’d also never call back if somebody I didn’t know left me a voicemail, or email back if I received an email like that from an address I don’t know. (For email that just gets trained as spam as soon as I can.)

    Circling back to that AI discussion in another thread, wouldn’t text message spam detection be a great feature for machine learning? It could go into a special section or tab that lets you look to make sure that the spam detection wasn’t a false positive. Here’s hoping that this is something that Apple is thinking about.

  18. Regarding US political parties text spam: My rule is to never give my mobile phone number to any politician. That means when I take part in writing letters to, or signing a petition to any politician, I never provide my mobile number. Why? As expected, these numbers are collected and either shared or sold. It’s the same old story, the same as email addresses. Since certain politicians demand a phone number, I originally used all 5s as the number. One of my politicians got wise to that, so I’ve had to become more creative. One thing not to do is type in a random number that could victimize a real person. I’ve had that happen to me, with junk sent using someone else’s name.

  19. The problem here, is that it’s perfectly legal and they are explicitly allowed to ignore your requests to unsubscribe.

    The most significant anti-spam law in the US is the CAN-SPAM act, but it has so many holes that it is practically useless. In particular:

    • It only applies to commercial communication. So messages from non-profits, survey companies and political campaigns have no restrictions.
    • It’s strictly opt-out. A sender is allowed to send to anybody until they explicitly ask to be unsubscribed. And then they have 10 days to comply. And this doesn’t prevent them from selling/giving your contact information to anyone else - who can start spamming until you opt-out from them.
    • It is almost never actually enforced. So companies can give the finger to the recipients and know that they will probably never face any consequences.

    See also: Candid answers to CAN-SPAM questions | Federal Trade Commission

  20. I follow that same rule. Same goes with email addresses.

    Unfortunately, it appears at least here in CA it’s entirely legal for a voter registrar to hand over (or sell?) email addresses you gave to the voting authorities (for the purpose of the act of voting) to political parties and operatives.

    Fortunately for me I run my own mail server so I tend to give out specific email addresses for purposes like this. Once the email address I gave my county voter registrar started accumulating crap, I knew what they had done with my private information. So I just reconfigured my email server to route anything sent to that specific address to /dev/null. My loss is that the county registrar will no longer be able to get in touch with me on voting matters, I’ll survive. :wink: But I shudder thinking what happens to people who just use one private email address that they can’t just throw away. Either start fuzzing with server side spam control and reconfiguring spam rules or live with an ever growing onslaught of crap forever.

    IMHO It should never be legal for any government body to just pass on people’s personal information to some undisclosed private entity without having received explicit prior consent. Not legal mumbo jumbo boiler plate in 4-pt font size at the bottom of some form nobody reads. Actual written permission for every single instance before they pass it on. Blanket consent should never be a permissible default. Whatever happened to “lead by example”?

  21. Ditto in MN, but it includes street addresses, with no restriction that the purchaser be a political party or operative. John Doe can request and receive a list of all registered voters. (I believe it costs money, which might reduce the number of times that an address is released, but that raises its own conflict-of-interest issues.)

    Hear hear.

  22. The problem is that the laws were written before electronic communication. Most people don’t consider it an invasion of privacy to receive campaign literature in the mail, but that’s not really the case for phone calls, texts and e-mail - especially when received on mobile devices.

    In most places, the voter registry is a public record. And it that record usually includes what party each person is registered with and which elections they’ve voted in. And there are good reasons why it should be (e.g. watchdog groups looking to see if dead people are voting or if a person is registered in multiple locations simultaneously).

    But it is really inconvenient when the spammers use the records for their own purposes.

  23. I made it a hard policy that if any candidate spams me with text messages, I won’t vote for them. Several times in the past view years I didn’t vote for a candidate I was going to vote for because they spammed me.

    I have zero-tolerance for such behavior. They probably don’t care – I’m only one vote – but if enough people did that, maybe they’d stop.

  24. Do you tell the candidates you are doing this? Just wondering if any of them responded to you (and how).

  25. I actually replied to a few such texts that seemed to come from a real person (an agent acting as the candidate’s representative) and wrote something along the lines of, “Thanks for spamming me with this unsolicited text. Per my personal policy, I will never vote for a candidate that sends spam. I had planned on voting for you, but now I will not. You have made my decision for me.”

    The responses I got ranged from nothing to a generic “I’m sorry to hear that.” None ever apologized or promised to stop spamming.

    After that I just started reporting those text as junk as clearly they don’t care about my feedback.

  26. I’ve been a Nomorobo user for years, but I had never tried their spam text filter (I think that in the old days, it required giving them access to your Contacts).

    I recently enabled it, and I have found that while it does in fact send spammy messages to the Junk folder, and will allow me to delete the messages from the Junk folder, days later I open Messages and voila—the same message I thought I had deleted is now sitting there in the All Messages folder, as if brand-spanking new.

    Anyone else seen this? I regard it as worse than useless.

  27. Nomorobo sends most of my spam texts to the Junk folder, but it misses some, which end up in the Unknown Senders folder. When I look in All Messages, I see both Known and Unknown Senders, but not Junk. I think this is correct behavior.

    I stick to Known Messages, unless I’m specifically looking for something like a DoorDash text.

    If messages from Junk are showing up in your All Messages, I’d guess that is an Apple bug, not Nomorobo.

  28. I’m diligent about reporting all spam texts, not just political ones.

    Do you have any indication that doing so makes any difference?

  29. The question I asked was what happens when you delete messages from Junk.

  30. I don’t delete the messages in my Junk folder, I’ve just been letting them pile up, since they don’t impact me.

    If they do show up again in All Messages, I’d guess that’s an Apple bug. I don’t think Nomorobo is called again once the messages are sorted.

    You could report it with Apple’s bug reporter.

  31. Thanks for your suggestion, but I don’t have time to troubleshoot bugs. I would have been interested in seeing if anyone else saw the same behavior, or if it’s just me.

    Here’s another issue: Nomorobo recommends that if a text is mistakenly filtered as Spam, the remedy is to add the sender to Contacts. In fact, I see no other way to get something out of the Junk folder (except of course to delete it, then wait a few days to see if it returns). Unfortunately, there are a lot of texts I get from numbers I don’t really want in my Contacts.

    Based on my brief trial, I can’t recommend Nomorobo for filtering spam texts, and I will be turning this feature off.

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