Improper Control of Interaction Frequency

Description

This can allow the actor to perform actions more frequently than expected. The actor could be a human or an automated process such as a virus or bot. This could be used to cause a denial of service, compromise program logic (such as limiting humans to a single vote), or other consequences. For example, an authentication routine might not limit the number of times an attacker can guess a password. Or, a web site might conduct a poll but only expect humans to vote a maximum of once a day.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

In the following code a username and password is read from a socket and an attempt is made to authenticate the username and password. The code will continuously checked the socket for a username and password until it has been authenticated.

char username[USERNAME_SIZE];
char password[PASSWORD_SIZE];

while (isValidUser == 0) {

  if (getNextMessage(socket, username, USERNAME_SIZE) > 0) {
    if (getNextMessage(socket, password, PASSWORD_SIZE) > 0) {
      isValidUser = AuthenticateUser(username, password);
    }
  }

}
return(SUCCESS);

This code does not place any restriction on the number of authentication attempts made. There should be a limit on the number of authentication attempts made to prevent brute force attacks as in the following example code.

int count = 0;
while ((isValidUser == 0) && (count < MAX_ATTEMPTS)) {

  if (getNextMessage(socket, username, USERNAME_SIZE) > 0) {
    if (getNextMessage(socket, password, PASSWORD_SIZE) > 0) {
      isValidUser = AuthenticateUser(username, password);
    }
  }
  count++;

}
if (isValidUser) {
  return(SUCCESS);
}
else {
  return(FAIL);
}

See Also