An information processing apparatus includes a clustering unit configured to read messages from a log and to classify the read messages into clusters according to similarities of the messages; a variable portion finding unit configured to find a portion variable between messages; an attribute determination unit configured to estimate and determine a confidential attribute of the variable portion by using predefined rule; and an attribute estimation unit configured to, in a case where there is a portion whose confidential attribute is undeterminable by using the rules, estimate the confidential attribute of the portion having the undeterminable confidential attribute with use of either a correspondence between appearance locations in the messages, or a co-appearance relation of a portion having a determined confidential attribute and the portion having the undeterminable confidential attribute.