Most people who use e-mail now know enough to be on guard against “phishing” messages that pretend to be from a bank or business but are actually attempts to steal passwords and other personal information. In some countries, like Brazil, it has been eclipsed by an even more virulent form of electronic con — the use of keylogging programs that silently copy the keystrokes of computer users and send that information to the crooks. These programs are often hidden inside other software and then infect the machine, putting them in the category of malicious programs known as Trojan horses, or just Trojans. Two weeks ago, Brazilian federal police descended on the northern city of Campina Grande and several surrounding states, and arrested 55 people — at least 9 of them minors — for seeding the computers of unwitting Brazilians with keyloggers that recorded their typing whenever they visited their banks online.The fraud ring stole about $4.7 million from 200 different accounts at six banks since it began operations last May, according to the Brazilian police. The twist here is that the keylogging programs exploit security flaws and monitor the path that carries data from the keyboard to other parts of the computer.