1. Заходим в папку Steam\steamapps\common\alien swarm\swarm\cfg и создаём файл server.cfg
с таким содержанием
hostname "Servername"
sv_allowdownload 1
sv_allowupload 1
rcon_password "RCONpass"
sv_rcon_banpenalty 10
sv_rcon_maxfailures 5
net_maxfilesize "200"
sv_logbans 1
exec banned_ip.cfg
exec banned_user.cfg
writeid
writeip
sv_lan 0
asw_ignore_need_two_player_requirement 1

2. запускаем сервер и выполняем exec server.cfg
3. Можно сделать так, чтобы монстры ходили медленно, а люди очень быстро, для этого редактируем файл difficulty.cfg , который находится по адресу Steam\steamapps\common\alien swarm\swarm\cfg
Стандартная настройка (по умолчанию)
// Alien modifiers for difficulty level
// Base mission difficulty is:
// Easy = 3
// Normal = 5
// Hard = 7
// Insane = 10
// With campaign map modifers affecting this number (-2 to +2)
// Alien health and damage modifiers are applied for every step away from
// the base mission difficulty level of 5.
// 20% extra health for every difficulty above 5
asw_difficulty_alien_health_step "0.2"
// 20% extra damage for every difficulty above 5
asw_difficulty_alien_damage_step "0.2"
// Speed modifiers for different difficulty levels:
asw_marine_speed_scale_easy "0.96"
asw_marine_speed_scale_normal "1.0"
asw_marine_speed_scale_hard "1.024"
asw_marine_speed_scale_insane "1.048"
asw_alien_speed_scale_easy "0.7"
asw_alien_speed_scale_normal "1.0"
asw_alien_speed_scale_hard "1.1"
asw_alien_speed_scale_insane "1.2"
Монстры ходят медленно, а люди очень быстро:
// Alien modifiers for difficulty level
// Base mission difficulty is:
// Easy = 3
// Normal = 5
// Hard = 7
// Insane = 10
// With campaign map modifers affecting this number (-2 to +2)
// Alien health and damage modifiers are applied for every step away from
// the base mission difficulty level of 5.
// 20% extra health for every difficulty above 5
asw_difficulty_alien_health_step "0.2"
// 20% extra damage for every difficulty above 5
asw_difficulty_alien_damage_step "0.2"
// Speed modifiers for different difficulty levels:
asw_marine_speed_scale_easy "10"
asw_marine_speed_scale_normal "10"
asw_marine_speed_scale_hard "10"
asw_marine_speed_scale_insane "10"
asw_alien_speed_scale_easy "0"
asw_alien_speed_scale_normal "0"
asw_alien_speed_scale_hard "0"
asw_alien_speed_scale_insane "0"