‫So although we stored the passwords with a strong encryption algorithm, it's still not safe to let
‫just anyone access the password hashes because they're still open to the offline password cracking attacks.
‫So it's possible to identify access control lists for the communications services such as an MP, as
‫I say, can tell that with these access lists, we can decide who can and cannot connect to the services,
‫then close the services for everybody else.
‫So there are two types of access lists, standard and extended.
‫Let's have a look.
‫We can see how we can manage the access to the router.
‫So once again, we are back in the network here we created by using Genesis three, all the devices
‫are still active and running.
‫That's always a good time.
‫Over the routers console.
‫And enter the config terminal mode.
‫Access list is the key word to create and configure access control list.
‫So put a question mark to see the options.
‫The number here decides the type of the access list will make an example of standard access.
‫So just put a number between one and 99.
‫I'll just put two.
‫A standard access control list either denies or permits source IP addresses.
‫In addition, a source IP addresses and extended access control, this can also deny or permit based
‫on destination IP addresses, ports and those services as well.
‫Question mark again.
‫And these are the options we can either deny or permit a connection request.
‫So let's decide who to permit first question mark to see the options.
‫OK.
‫We can put a pattern here, so the computers matching the pattern are allowed.
‫If we use any year, that means we permit all computers except ones which are identified by the deny
‫and the access list.
‫Alternatively, we can permit directly to any specified computer.
‫So here I'll use host as the option and let my colleague access to it.
‫So let me look at the IP address of the Kali 10.3.
‫I want to deny all others, so access list to deny any.
‫Now, the next thing we have to do is go to the line the DIY and apply this access list to the interface.
‫Good, so tip line y zero four to enter line config.
‫In the line config, we'll use access list command.
‫Number of access list first and now a question mark to see the options and look at that, there are
‫two options in and out.
‫Now, since we're going to be telnet into the router, we're going to use in.
‫Exit or control C to exit from the line config mode.
‫Now I want you to see the running conflict, so type, show, run.
‫And here is the running config, so scrolling down.
‫Showing the access list and make sure that everything's right.
‫So here it is.
‫And yes, as you can see, we have our access list to to permit Carly and deny any other host attempting
‫to make a Telnet connection.
‫Now, let's test whether the access list works as intended.
‫So back in my network, I have other VR machines like like.
‫One of them is OWASP, BWC, as you know, and its IP address is 10.4.
‫First, I want to check if the network is OK, and OWASP sees the router so ping one nine two two one
‫six eight one zero two one.
‫And sure enough, we have the replies.
‫Now I want to create a Telnet connection to the router, so take Telnet and the router IP hit enter.
‫Connection is refused.
‫Well, that's what's supposed to be right.
‫That means the deny part of the access list is working properly.
‫What about the permit part?
‫So go to Carl in terminal screen, telnet into the router and as you can see, we can telnet into the
‫router.
‫The request is not refused and we are allowed to telnet from Carly.
‫So to double check, I'll run an end map query to check whether the Telnet port of the router is open.
‫And yes, of course it is.