dos.awk

function max(arr, big) {
    big = 0;
    for (i in cat) {
        if (cat[i] > big) { big=cat[i]; }
    }
    return big
}

NF > 0 {
    cat[$1]++;
}
END {
    maxm = max(cat);
    for (i in cat) {
        scaled = 60 * cat[i] / maxm;
        printf "%-25.25s  [%8d]:", i, cat[i]
        for (i=0; i<scaled; i++) {
            printf "#";
        }
        printf "\n";
    }
}

Count IP hits from webserver logs
usage
cat /var/log/access.log|awk -f /home/raldea/dos.awk | sort -nrk3|less