(MONEY Magazine) – Credit-card issuers send out reams, heaps, mountains of junk mail, but guess what? Some of it is useful. Buried inside those teeny-type brochures on your privacy rights (the ones you get every year but swiftly trash because, c'mon, who can possibly read them?) is valuable info about who's snooping around your account, what you can do to stop it and how you can get off certain mailing lists. That's right: junk mail that can head off future junk mail.

• BANKS CAN SHARE details about you (like your account number, Social Security digits, income, assets, debts) with what are called affiliated companies. These can number in the hundreds if it's a major bank and can include brokerages, insurers, credit-card units and assorted lenders. Banks don't have to name their affiliates, but some (like Bank of America) do. Scan the statement for the word affiliated.

• YOU CAN'T PREVENT your bank from sharing with affiliates, but you can limit what it shares. You can restrict information about your creditworthiness, including your credit score. And you can stop any further sharing with nonaffiliates like telemarketers. Speed-read those privacy statements for the 800 phone number you can call to opt out. --ETELKA LEHOCZKY