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The short answer
USSD banking is tied to your SIM, so anyone who gets your SIM or your phone number and knows or guesses your USSD PIN may be able to move money. Protect it with a USSD PIN nobody could guess, a low USSD limit if your bank lets you set one, a SIM PIN, and fast action if your line goes dead. Save your bank's official emergency blocking instructions now, before you need them.
Why USSD is convenient and risky
USSD lets you check balances, buy airtime and send money by dialling a short code, with no data and on any phone. For millions of Nigerians it is the main way to bank. The same feature that makes it convenient is the risk: USSD recognises you by your SIM. There is no separate app to get past, so whoever holds the SIM, plus your USSD PIN, holds the account. That does not mean you should stop using it; it means the PIN and the SIM need more care than most people give them.
How USSD fraud happens
| Route | What happens |
|---|---|
| Stolen phone or SIM | Thief puts your SIM in any phone and dials your bank's code |
| SIM swap | Fraudster gets your number moved to their SIM; see SIM swap fraud |
| Guessed USSD PIN | PIN is a birthday, 1234 or the last digits of your phone number |
| Watched PIN | Someone sees you type it, or you told them |
| Phone left with someone | A relative, repairer or colleague dials a transfer while you are away |
| Scam instructions | A caller tells you to dial a code that actually sends money |
The last one deserves attention. A fraudster on the phone may read out a string of digits and ask you to dial it 'to stop a fraud' or 'to receive your prize'. The string is a transfer to their account. Never dial a code someone else gives you.
SIM swap and USSD
Because USSD depends on your number, a SIM swap is especially dangerous for USSD users. The NCC requires NIN verification for SIM replacement, done by networks or licensed agents, but fraud still happens. See SIM swap fraud for the signs.
Settings that protect you
- Set a strong USSD PIN, different from your card PIN and app PIN, and with no link to your dates or phone number. See choosing a transaction PIN.
- Ask your bank about USSD limits and set a lower daily limit if you rarely send large amounts this way.
- Turn on a SIM PIN in your phone's settings, so a stolen SIM cannot be used in another phone without it.
- Lock your phone with a PIN, not just a pattern.
- Save your bank's emergency block instructions. Many Nigerian banks publish a code or number to block your account quickly. Get yours from the bank's official website or branch and write it down somewhere away from your phone.
- Clear USSD messages where your phone stores them, and do not leave the phone with strangers.
- Keep alerts on, ideally by email as well as SMS, so you hear about debits even if your SIM is taken.
Worked example
Example only. Grace, a trader, uses USSD for most payments. Her phone is stolen at a bus stop. Her USSD PIN was 0000, the default she never changed. Within 20 minutes, ₦60,000 is sent out through USSD. She borrows a phone, calls her bank and blocks the account, then reports to the police. With her new SIM she sets a six-digit USSD PIN, asks her bank to lower her USSD daily limit, turns on a SIM PIN and writes her bank's emergency block instructions on a card she keeps at home.
If someone is using your USSD
- Block your account through your bank's official emergency channel or fraud line.
- Call your network to block the SIM.
- List the transactions and the receiving accounts.
- Follow our first-hour fraud plan, and if your bank does not resolve your complaint, escalate to the CBN.
Helping older relatives with USSD
Parents and grandparents who bank only by USSD are frequent targets of phone scams that ask them to dial codes. Sit with them once to change any default PIN, set a lower limit, and write down the bank's official block instructions in large print. Agree a simple rule: they never dial a code someone reads to them on a call, and they ring you first if anyone says their account is in danger. Make sure they know that a real bank will never ask them to dial anything to 'stop' a fraud.
When to use something else
USSD is useful when you have no data or only a basic phone. For larger payments, an app that needs an authenticator code and a transaction PIN is harder to abuse than a channel that relies only on your SIM. Many people keep USSD for small everyday payments and use an app for anything bigger. Our comparison of authenticator apps and SMS codes explains why codes tied to your number are the weak point.
Where Pryme fits
Pryme works through its app, with every payment approved by an authenticator app and your transaction PIN, not by your SIM or SMS codes. That means someone holding your phone number alone cannot move money from your Pryme account. See security.
Questions people ask
Can someone use my USSD without my phone?
Only if they get your number onto their SIM through a SIM swap and know your USSD PIN. That is why a strong PIN and quick action on a dead line matter.
How do I block my USSD banking?
Use your bank's official emergency block code or fraud line. Get the instructions from your bank's website or a branch and save them now.
Is USSD banking safe?
It is reasonably safe with a strong PIN, low limits and a SIM PIN, but it is only as safe as your SIM. Use an app with an authenticator for larger amounts.
Should I change my default USSD PIN?
Yes, immediately, to a PIN not linked to your dates, phone number or simple patterns.
Sources
- NCC: NCC demands MNOs, agents, consumers comply with SIM Replacement Guidelines · accessed Oct 2026
- NCC: Guidelines on SIM Replacement · accessed Oct 2026
- US FTC: SIM swap scams, how to protect yourself · accessed Oct 2026
- CBN: Consumer Protection, how to lodge a complaint · accessed Oct 2026
This article is general information, not financial, legal or tax advice. Products described are provided under the terms on this site and are subject to regulation and eligibility.