Hello all,
I have an application that accepts a lot of user data and I want to be a safe and secure as possible. At no time does anything supplied by the user used in any system or exec commands.

Most of the incoming data is either used for program descisions or saved in a flat file database.

OK, now the question. Do you consider the following code to be secure and hacker proof?
If not, why not and how can I improve it.
@special = ("body",
            "subject",
            "link_url",
            "pid");

foreach $field (keys %form_data) {
    # specific fields that can have additional characters
    if($field eq "body" ||
       $field eq "subject" ||
       $field eq "link_url" ||
       $field eq "pid") {
        # were looking for specific hacker tricks here
        foreach (@special) {
            $form_data{$_} =~ s/system\(.+//g;
            $form_data{$_} =~ s/grep//g;
            $form_data{$_} =~ s/\srm\s//g;
            $form_data{$_} =~ s/\srf\s//g;
            $form_data{$_} =~ s/\.\.([\/\:]|$)//g;
            $form_data{$_} =~ s/< *((SCRIPT)|(APPLET)|(EMBED))[^>]+>//
+ig;
        }
    # all other fields get sifted here
    } elsif($form_data{$field} ne "") {
        unless ($form_data{$field} =~ /^([-\@\w.\s]+)$/) {
            # exit handler here
        }
    }
}

[download]
Thanks in advance
-- Brian

In reply to Opinions needed on CGI security by Gryphaan

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