Watcher是用於linux系統的，通常你只需要在命令行後臺運行它就可以了，它的參數如下：
Usage: watcher [參數]
-d device 將'device'設定爲當前的網卡，默認爲第一個non-loopback的interface
-f flood 設定接收到多少不完全的連接後才認爲是flood的攻擊
-h 幫助信息
-i icmplimit 設定接收到多少icmp echo replies就認爲是smurf攻擊
-m level 可以設定監控的機器，比如subnet爲子域中的機器，或者all爲所有
-p portlimit 在timeout的限制時間內有多少端口接收到信息包算是一次端口掃描
-r reporttype 如果reporttype設爲dos，那麼只有拒絕服務攻擊會被記錄，如果是scan
的話，只有掃描行爲會被記錄，默認則記錄所有東西
-t timeout 每隔timeout的時間就記錄信息包並打印出潛在的攻擊行爲
-w webcount 設定我們從80口接收到多少信息包纔算是一次端口掃描(cgi)
希望這個小玩意能使你的系統稍微安全一些，但是得警告你的是，系統安全是多方面的，別
指望一個應用程序或者什麼東西能使你絕對安全——如果你不信，遲早都得重裝系統的;)
<++> EX/Watcher.c
/*********************************************************************
Program: watcher
A network level monitoring tool to detect incoming packets indicative of
potential attacks.
This software detects low level packet scanners and several DOS attacks.
Its primary use is to detect low level packet scans, since these are usually
done first to identify active systems and services to mount further attacks.
The package assumes every incoming packet is potentially hostile. Some checks
are done to minimize false positives, but on occasion a site may be falsely
identified as having performed a packet scan or SYNFLOOD attack. This usually
occurs if a large number of connections are done in a brief time right before
the reporting timeout period (i.e. when browsing a WWW site with lots of
little GIF's, each requiring a connection to download). You can also get false
positives if you scan another site, since the targets responses will be viewed
as a potential scan of your system.
By default, alerts are printed to SYSLOG every 10 seconds.
***********************************************************************/
#include <stdio.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <malloc.h>
#include <netinet/tcp.h>
#include <netinet/in_systm.h>
#include <net/if_arp.h>
#include <net/if.h>
#include <netinet/udp.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <linux/if_ether.h>
#include <syslog.h>
#define PKTLEN 96 /* Should be enough for what we want */
#ifndef IP_MF
#define IP_MF 0x2000
#endif
/***** WATCH LEVELS ******/
#define MYSELFONLY 1
#define MYSUBNET 2
#define HUMANITARIAN 3
/***** REPORT LEVELS *****/
#define REPORTALL 1
#define REPORTDOS 2
#define REPORTSCAN 3
struct floodinfo
{
u_short sport;
struct floodinfo *next;
};
struct addrlist
{
u_long saddr;
int cnt;
int wwwcnt;
struct addrlist *next;
};
struct atk
{
u_long saddr;
u_char eaddr[ETH_ALEN];
time_t atktime;
};
struct pktin
{
u_long saddr;
u_short sport;
u_short dport;
time_t timein;
u_char eaddr[ETH_ALEN];
struct floodinfo *fi;
struct pktin *next;
};
struct scaninfo
{
u_long addr;
struct atk teardrop;
struct atk land;
struct atk icmpfrag;
struct pktin *tcpin;
struct pktin *udpin;
struct scaninfo *next;
u_long icmpcnt;
} ;
struct scaninfo *Gsilist = NULL, *Gsi;
u_long Gmaddr;
time_t Gtimer = 10, Gtimein;
int Gportlimit = 7;
int Gsynflood = 8;
int Gwebcount = 40;
int Gicmplimit = 5;
int Gwatchlevel = MYSELFONLY;
int Greportlevel = REPORTALL;
char *Gprogramname, *Gdevice = "eth0";
/******** IP packet info ********/
u_long Gsaddr, Gdaddr;
int Giplen, Gisfrag, Gid;
/****** Externals *************/
extern int errno;
extern char *optarg;
extern int optind, opterr;
void do_tcp(), do_udp(), do_icmp(), print_info(), process_packet();
void addtcp(), addudp(), clear_pktin(), buildnet();
void doargs(), usage(), addfloodinfo(), rmfloodinfo();
struct scaninfo *doicare(), *addtarget();
char *anetaddr(), *ether_ntoa();
u_char *readdevice();
main(argc, argv)
int argc;
char *argv[];
{
int pktlen = 0, i, netfd;
u_char *pkt;
char hostname[32];
struct hostent *hp;
time_t t;
doargs(argc, argv);
openlog("WATCHER", 0, LOG_DAEMON);
if(gethostname(hostname, sizeof(hostname)) < 0)
{
perror("gethostname");
exit(-1);
}
if((hp = gethostbyname(hostname)) == NULL)
{
fprintf(stderr, "Cannot find own address/n");
exit(-1);
}
memcpy((char *)&Gmaddr, hp->h_addr, hp->h_length);
buildnet();
if((netfd = initdevice(O_RDWR, 0)) < 0)
exit(-1);
/* Now read packets forever and process them. */
t = time((time_t *)0);
while(pkt = readdevice(netfd, &pktlen))
{
process_packet(pkt, pktlen);
if(time((time_t *)0) - t > Gtimer)
{
/* Times up. Print what we found and clean out old stuff. */
for(Gsi = Gsilist, i = 0; Gsi; Gsi = Gsi->next, i++)
{
clear_pktin(Gsi);
print_info();
Gsi->icmpcnt = 0;
}
t = time((time_t *)0);
}
}
/**********************************************************************
Function: doargs
Purpose: sets values from environment or command line arguments.
**********************************************************************/
void doargs(argc, argv)
int argc;
char **argv;
{
char c;
Gprogramname = argv[0];
while((c = getopt(argc,argv,"d:f:hi:m:p:r:t:w:")) != EOF)
{
switch(c)
{
case 'd':
Gdevice = optarg;
break;
case 'f':
Gsynflood = atoi(optarg);
break;
case 'h':
usage();
exit(0);
case 'i':
Gicmplimit = atoi(optarg);
break;
case 'm':
if(strcmp(optarg, "all") == 0)
Gwatchlevel = HUMANITARIAN;
else if(strcmp(optarg, "subnet") == 0)
Gwatchlevel = MYSUBNET;
else
{
usage();
exit(-1);
}
break;
case 'p':
Gportlimit = atoi(optarg);
break;
case 'r':
if(strcmp(optarg, "dos") == 0)
Greportlevel = REPORTDOS;
else if(strcmp(optarg, "scan") == 0)
Greportlevel = REPORTSCAN;
else
{
exit(-1);
}
break;
case 't':
Gtimer = atoi(optarg);
break;
case 'w':
Gwebcount = atoi(optarg);
break;
default:
usage();
exit(-1);
}
}
}
/**********************************************************************
Function: usage
Purpose: Display the usage of the program
**********************************************************************/
void usage()
{
printf("Usage: %s [options]/n", Gprogramname);
printf(" -d device Use 'device' as the network interface device/n");
printf(" The first non-loopback interface is the default/n");
printf(" -f flood Assume a synflood attack occurred if more than/n");
printf(" 'flood' uncompleted connections are received/n");
printf(" -h A little help here/n");
printf(" -i icmplimit Assume we may be part of a smurf attack if more/n");
printf(" than icmplimit ICMP ECHO REPLIES are seen/n");
printf(" -m level Monitor more than just our own host./n");
printf(" A level of 'subnet' watches all addresses in our/n");
printf(" subnet and 'all' watches all addresses/n");
printf(" -p portlimit Logs a portscan alert if packets are received for/n");
printf(" more than portlimit ports in the timeout period./n");
printf(" -r reporttype If reporttype is dos, only Denial Of Service/n");
printf(" attacks are reported. If reporttype is scan/n");
printf(" then only scanners are reported. Everything is/n");
printf(" reported by default./n");
printf(" -t timeout Count packets and print potential attacks every/n");
printf(" timeout seconds/n");
printf(" -w webcount Assume we are being portscanned if more than/n");
printf(" webcount packets are received from port 80/n");
}
/**********************************************************************
Function: buildnet
Purpose: Setup for monitoring of our host or entire subnet.
**********************************************************************/
void buildnet()
{
u_long addr;
u_char *p;
int i;
if(Gwatchlevel == MYSELFONLY) /* Just care about me */
{
(void) addtarget(Gmaddr);
}
else if(Gwatchlevel == MYSUBNET) /* Friends and neighbors */
{
addr = htonl(Gmaddr);
addr = addr & 0xffffff00;
for(i = 0; i < 256; i++)
(void) addtarget(ntohl(addr + i));
}
}
/**********************************************************************
Function: doicare
Purpose: See if we monitor this address
**********************************************************************/
struct scaninfo *doicare(addr)
u_long addr;
{
struct scaninfo *si;
int i;
for(si = Gsilist; si; si = si->next)
{
if(si->addr == addr)
return(si);
}
if(Gwatchlevel == HUMANITARIAN) /* Add a new address, we always care */
{
si = addtarget(addr);
return(si);
}
return(NULL);
}
/**********************************************************************
Function: addtarget
Purpose: Adds a new IP address to the list of hosts to watch.
**********************************************************************/
struct scaninfo *addtarget(addr)
u_long addr;
{
struct scaninfo *si;
if((si = (struct scaninfo *)malloc(sizeof(struct scaninfo))) == NULL)
{
perror("malloc scaninfo");
exit(-1);
}
memset(si, 0, sizeof(struct scaninfo));
si->addr = addr;
si->next = Gsilist;
Gsilist = si;
return(si);
}
/**********************************************************************
Function: process_packet
Purpose: Process raw packet and figure out what we need to to with it.
Pulls the packet apart and stores key data in global areas for reference
by other functions.
**********************************************************************/
void process_packet(pkt, pktlen)
u_char *pkt;
int pktlen;
{
struct ethhdr *ep;
struct iphdr *ip;
static struct align { struct iphdr ip; char buf[PKTLEN]; } a1;
u_short off;
Gtimein = time((time_t *)0);
ep = (struct ethhdr *) pkt;
if(ntohs(ep->h_proto) != ETH_P_IP)
return;
pkt += sizeof(struct ethhdr);
pktlen -= sizeof(struct ethhdr);
memcpy(&a1, pkt, pktlen);
ip = &a1.ip;
Gsaddr = ip->saddr;
Gdaddr = ip->daddr;
if((Gsi = doicare(Gdaddr)) == NULL)
return;
off = ntohs(ip->frag_off);
Gisfrag = (off & IP_MF); /* Set if packet is fragmented */
Giplen = ntohs(ip->tot_len);
Gid = ntohs(ip->id);
pkt = (u_char *)ip + (ip->ihl << 2);
Giplen -= (ip->ihl << 2);
switch(ip->protocol)
{
case IPPROTO_TCP:
do_tcp(ep, pkt);
break;
case IPPROTO_UDP:
do_udp(ep, pkt);
break;
case IPPROTO_ICMP:
do_icmp(ep, pkt);
break;
default:
break;
}
}
/**********************************************************************
Function: do_tcp
Purpose: Process this TCP packet if it is important.
**********************************************************************/
void do_tcp(ep, pkt)
struct ethhdr *ep;
u_char *pkt;
{
struct tcphdr *thdr;
u_short sport, dport;
thdr = (struct tcphdr *) pkt;
if(thdr->th_flags & TH_RST) /* RST generates no response */
return; /* Therefore can't be used to scan. */
sport = ntohs(thdr->th_sport);
dport = ntohs(thdr->th_dport);
if(thdr->th_flags & TH_SYN)
{
if(Gsaddr == Gdaddr && sport == dport)
{
Gsi->land.atktime = Gtimein;
Gsi->land.saddr = Gsaddr;
memcpy(Gsi->land.eaddr, ep->h_source, ETH_ALEN);
}
}
addtcp(sport, dport, thdr->th_flags, ep->h_source);
}
/**********************************************************************
Function: addtcp
Purpose: Add this TCP packet to our list.
**********************************************************************/
void addtcp(sport, dport, flags, eaddr)
u_short sport;
u_short dport;
u_char flags;
u_char *eaddr;
{
struct pktin *pi, *last, *tpi;
/* See if this packet relates to other packets already received. */
for(pi = Gsi->tcpin; pi; pi = pi->next)
{
if(pi->saddr == Gsaddr && pi->dport == dport)
{
if(flags == TH_SYN)
addfloodinfo(pi, sport);
else if((flags & TH_FIN) || (flags & TH_ACK))
rmfloodinfo(pi, sport);
return;
}
last = pi;
}
/* Must be new entry */
if((tpi = (struct pktin *)malloc(sizeof(struct pktin))) == NULL)
{
perror("Malloc");
exit(-1);
}
memset(tpi, 0, sizeof(struct pktin));
memcpy(tpi->eaddr, eaddr, ETH_ALEN);
tpi->saddr = Gsaddr;
tpi->sport = sport;
tpi->dport = dport;
tpi->timein = Gtimein;
if(flags == TH_SYN)
addfloodinfo(tpi, sport);
if(Gsi->tcpin)
last->next = tpi;
else
Gsi->tcpin = tpi;
}
/**********************************************************************
Function: addfloodinfo
Purpose: Add floodinfo information
**********************************************************************/
void addfloodinfo(pi, sport)
struct pktin *pi;
u_short sport;
{
struct floodinfo *fi;
fi = (struct floodinfo *)malloc(sizeof(struct floodinfo));
if(fi == NULL)
{
perror("Malloc of floodinfo");
exit(-1);
}
memset(fi, 0, sizeof(struct floodinfo));
fi->sport = sport;
fi->next = pi->fi;
pi->fi = fi;
}
/**********************************************************************
Function: rmfloodinfo
Purpose: Removes floodinfo information
**********************************************************************/
void rmfloodinfo(pi, sport)
struct pktin *pi;
u_short sport;
{
struct floodinfo *fi, *prev = NULL;
for(fi = pi->fi; fi; fi = fi->next)
{
if(fi->sport == sport)
break;
prev = fi;
}
if(fi == NULL)
return;
if(prev == NULL) /* First element */
pi->fi = fi->next;
else
prev->next = fi->next;
free(fi);
}
}