随着网络的普及，我们的生活越来越方便，但是网络安全也成了很多人面临的一个问题。特别是那些有着商业数据的企业电脑，更要注意上网安全常识，不然病毒会对我们造成严重的威胁。
vnc所有帐号登陆的时候： 1.加入ip到一个列表（黑名单）， 并记录时间， 在这个时间上＋10s钟作为下一次连接拒绝时间。 2.登陆次数限制， 如果失败超过5次， 则加入黑名党， 再等10s后才能登陆。 请 ...
vnc所有帐号登陆的时候：
1.加入ip到一个列表（黑名单）， 并记录时间， 在这个时间上＋10s钟作为下一次连接拒绝时间。
2.登陆次数限制， 如果失败超过5次， 则加入黑名党， 再等10s后才能登陆。
请看下面代码：
void
vncServer::AddAuthHostsBlacklist(const char *machine)
{
omni_mutex_lock l(m_clientsLock);
// -=- Is the specified host blacklisted?
vncServer::BlacklistEntry *current = m_blacklist;
// Get the current time as a 64-bit value
SYSTEMTIME systime;
FILETIME ftime;
LARGE_INTEGER now;
GetSystemTime(&systime);
SystemTimeToFileTime(&systime, &ftime);
now.LowPart=ftime.dwLowDateTime;now.HighPart=ftime.dwHighDateTime;
now.QuadPart /= 10000000; // Convert it into seconds
while (current)
{
// Is this the entry we're interested in?
if (_stricmp(current->_machineName, machine) == 0)
{
// If the host is already blocked then ignore
if (current->_blocked)
return;
// Set the RefTime & failureCount
current->_lastRefTime.QuadPart = now.QuadPart + 10;
current->_failureCount++;
if (current->_failureCount > 5)
current->_blocked = TRUE;
判定函数代码：
while (current)
{
// Has the blacklist entry timed out?
if ((now.QuadPart - current->_lastRefTime.QuadPart) > 0) {////当前时间超过隔离时间？即如果10s钟后
// Yes. Is it a "blocked" entry?
if (current->_blocked)
{
// Yes, so unblock it & re-set the reference time
current->_blocked = FALSE; ///超过10s， 解除黑名单
current->_lastRefTime.QuadPart = now.QuadPart + 10;
} else
{
// No, so remove it
if (divvious)
divvious->_next = current->_next;
else
m_blacklist = current->_next;
vncServer::BlacklistEntry *next = current->_next;
free(current->_machineName);
delete current;
current = next;
continue;
}
}
// Is this the entry we're interested in?
if ((_stricmp(current->_machineName, hostname) == 0) &&/////比较是否再黑名单里面
(current->_blocked))
{
// Machine is blocked, so just reject it
vnclog.Print(LL_CONNERR, VNCLOG("client %s rejected due to blacklist entry\n"), hostname);
return vncServer::aqrReject;
}
divvious = current;
current = current->_next;
}
// Has a hostname been specified?
if (hostname == 0) {
vnclog.Print(LL_INTWARN, VNCLOG("verify failed - null hostname\n"));
return vncServer::aqrReject;
}
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以上原因决定了vnc弱口令扫描的特点：
1.密码最多只能超过5次出错， 然后就会被锁定， 需要10s钟解锁。
2.出错超过5次后每猜解一个密码， 都会被锁定， 所以后面的密码猜解非常慢（每一个隔10s）。