It is OK to share the last 4 digits of your social security number with a legit company or person that needs the lat 4 digits.
You just need to be careful when giving out the last 4 digits of your social security number as sometimes people as dishonest people can find out the other numbers in your social security number if they work hard enough.
If your SSN is compromised you should file a police report and contact the Social Security Administration right away to report it.
If your SSN is compromised the Social Security Administration to request a block on the SSN.
If you know your Social Security information has been compromised, you can request to Block Electronic Access.
This is done by calling the Social Security Administrations National 800 number (Toll Free 1-800-772-1213 or at their TTY number at 1-800-325-0778).
Contact the Internal Revenue Service (IRS) at 1-800-908-4490 or visit them online, if you believe someone is using your SSN to work, get your tax refund, or other abuses involving taxes.
Order free credit reports annually from the three major credit bureaus (Equifax, Experian, and TransUnion).
You can lock your SSN by calling the Social Security Administration or by creating an E-Verify account.
Also, you can contact all three of the nationwide CRAs to place a freeze on your credit reports.
To block electronic access to your SSN, you have to call your local Social Security office or 1-800-772-1213.
Finally, you can turn on the SSN Self Lock online via the Department of Homeland Security's (DHS) “myE-Verify” website.