Banks are more scrupulous than industry in general about protecting the privacy of their customers, but their record still isn't good, according to a survey of the country's largest banks conducted by the University of Illinois for Prof. David F. Linowes, formerly chairman of the U.S. Privacy Protection Study Commission.

The study, the second in a series, is intended to provide data to support privacy legislation recommended by that commission. The Carter administration sent the "Fair Financial Information Practices Act," which establishes privacy safeguards for consumer records, to Capitol Hill last Oct. 2.

Questionnaires were sent to 130 of the top banks, with 34, or 26 percent, replying. In a similar survey last summer of companies on the Fortune magazine listing of the 500 largest industrial corporations, half of those questioned reported on how they do or do not safeguard personal employe records.

Although the identification of individual banks was kept secret, the information that the largest respondent had 14,000 employes means that at least one bank among America's top 10 was included.

Researchers asked the institutions about their policies on informing individuals about the records kept on them, on individual access to those records, and on authorization to collect and give out personal data to third parties. According to Linowes, the findings show that the belief of most Americans that the details of their finances are nobody's business but their own isn't true.

Three out of four banks fail to tell their customers about the information they routinely give to government agencies, four out of five don't tell customers about their policies in giving information to nongovernment sources and three out of four don't obtain authorization from customers before passing on financial information about them.

Industry as a whole has an even poorer record. A random sample of 15 questions asked shows that banks scored higher marks for protecting peoples' privacy more than twice as often as industry. For example, although all of the banks said they give personal financial information to credit grantors compared with 85 percent of the Fortune 500 firms surveyed, twice as many indusrialists as bankers said they would open their files to landlords, and 22 percent of the requests for information from charitable organizations would be honored by industry versus 18 percent by banks.

In general industry has a better score when it comes to customer relations. (The survey consistently refers to "individuals," but this is interpreted to refer to employe records maintained by industry and customer records kept by banks.) Whereas 28 percent of the industries questioned inform their employes of the types of files they have on them, only 18 percent of the banks queried do as much for customers. As for informing people of the uses for the data -- i.e., who gets to find out pertinent financial information about them -- fewer than one-third of the industrialists do so compared with 15 percent of the bankers.

One of the most startling revelations was that six banks, or 18 percent, use polygraph equipment to verify information about individuals. Less than 2 percent of the industries reporting do. One bank used lie detector tests 97 times. Asked if the tests were those given to prospective security guards, Linowes replied they were given to customers, presumably in the course of fraud investigations.

Fewer banks allow individual access to files about themselves (76 to 62 percent), but of those that do, more banks allow those permitted access to copy (60 to 50 percent) and correct (86 to 79 percent) any erroneous information. Banks also make sure two and a half times more frequently than does industry that the corrections are disseminated.

Banks are more apt than industry (82 to 78 percent) to obtain written permission from individuals before seeking information about them from third parties, and less apt than industry (50 to 67 percent) to do so without permission. Nevertheless nine banks out of 10 admitted there are times when they find it necessary to collect information without informing the subject.

Only one bank in four gets the customer's okay before disclosing the information. Banks are nearly three times as strict as industry at large (96 to 35 percent) when it comes to requiring the government to obtain a subpoena before they will give out any information on people. In the case of nongovernmental requests from credit grantors, neighbors, lawyers and others, only 39 percent of the banks demand a subpoena compared with 14 percent of the industries.