O desafio apresentava um endpoint digx.asisctf.com na categoria web, e dava algumas dicas que o a resposta poderia estar no comand dig, ou seja no dominio de onde a challenge era apresentado
deadcow@capthook:~$ dig digx.asisctf.com any +multiline +noall +answer
; <<>> DiG 9.10.3-P4-Debian <<>> digx.asisctf.com any +multiline +noall +answer
;; global options: +cmd
digx.asisctf.com. 300 IN A 192.81.223.250
digx.asisctf.com. 300 IN RRSIG A 7 3 300 (
20171007125525 20170907125525 182 asisctf.com.
aoO35AqtS3IBePvCKiH2FRauTzj2HZ8GgNdS44Z35vUm
qAxTfj2spP7s+JBGU3dytDSJ2PJZe4MqYTTOkHwEWu+M
/xvhCv4kVk5dM2uhvp3evVmQFhnMfLCPhu7XP6A39LVB
Zi3SfAKMqv7/GyoT9+qnUyMBLiIHmObwOlptEeSrBRLV
qT8vm7AIY7ZpuoreiY3vjbywrGIjrAqYG5puoppqSWGT
i9UD3pTEdnAZZZnElc0vJ7c+r6ENHmtF7riXvorR8RyB
ASkoXpI0uqsaE17IyYUKj1cHlstHB7FNtsygekk1fwtn
IM0u8qNHsWbZUEtODuR/vBkKPjMdLRlIfQ== )
deadcow@capthook:~$O dominio da challenge, era digx.asisctf.com, e dig -x resolve apenas por IP, na verdade ele me indica quando feito no dominio, os endpoints do root-servers, porem resolvi tentar para ver se achava alguma pista
deadcow@capthook:~$ dig -x 192.81.223.250
; <<>> DiG 9.10.3-P4-Debian <<>> -x 192.81.223.250
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1456
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;250.223.81.192.in-addr.arpa. IN PTR
;; ANSWER SECTION:
250.223.81.192.in-addr.arpa. 877 IN PTR airplane.asisctf.com.
;; Query time: 2 msec
;; SERVER: 67.207.67.3#53(67.207.67.3)
;; WHEN: Fri Sep 08 19:17:23 UTC 2017
;; MSG SIZE rcvd: 90
deadcow@capthook:~$acessando o endpoint http://airplane.asisctf.com ele me pedia para entrar em modo offline para ver a flag, acessando pelo celular em modo airplane, após um breve texto, a flag: ASIS{just_Go_Offline_When_you_want_to_be_creative!}