Security A. +1 means the Digimon checks one extra security card when it hits the player, so a single swing does the work of two. Multiple instances add up, which is why finishers stacked on the right inherited effects can take three or four checks in one attack. If you're building an aggro line, this is usually the effect that decides how many turns you actually need.
16-4. <Security A.> (※formerly <Security Attack>) 16-4-1. <Security A.> is a keyword effect where the Digimon with this effect will have a modified number of security checks according to the number specified for this effect. This is shown on cards using text such as <Security A. +1>. 16-4-2. <Security A.> effects are persistent effects. The number of security checks is modified as soon as the effect is applied. (Example: If a Digimon gained <Security A. +1> at the point when it performs a security check, it will perform 1 additional security check.) (For details, refer to 15-8-2 "Persistent Effects") 16-4-3. If 1 Digimon has multiple instances of <Security A.>, the number of security checks that can be performed is modified according to their numerical values. However, even if a card has multiple instances of <Security A.>, the effect isn't considered to be an effect with the combined values from <Security A.>. (Examples: If a Digimon has 2 instances of <Security A. +1>, the additional number of cards checked will be 2, but the Digimon isn't considered to have <Security A. +2>.) 16-4-4. Even if a negative value is the result of the number of security checks being modified, the actual number of security checks is 0.
Comprehensive Rules §16-4 — official rules page
From Bandai's card rulings. Each links to the card it was asked about.
If this card's ＜On Deletion＞ effect is activated on my opponent's turn, when does the ＜Security Attack -1＞ end?
It ends when the current turn ends.
asked about Tinkermon (BT6-031)
If after using this card's ＜Digiburst＞ effect, one of my Digimon without ＜Digiburst＞ becomes a Digimon with ＜Digiburst＞, does that Digimon gain ＜Security Attack +1＞?
Yes, this effect is applied as a Global Effect. If it satisfies the condition afterwards, it gains ＜Security Attack +1＞.
asked about Rosemon (BT5-057)
If after using this card's ＜Digiburst＞ effect, one of my Digimon with ＜Digiburst＞ becomes a Digimon without ＜Digiburst＞, does that Digimon keep the ＜Security Attack +1＞?
No, this effect is applied as a Global Effect. So if it no longer satisfies the condition then it no longer has the ＜Security Attack +1＞.
asked about Rosemon (BT5-057)
If after using this card's ＜Digiburst＞ effect, this card leaves the battle area does the ＜Security Attack +1＞ continue being applied?
Yes, as it has already resolved and applied a Global effect, the Global effect continues applying even after Rosemon leaves the battle area.
asked about Rosemon (BT5-057)
If my opponent has no Digimon in play but reveals a [ST8-06]/[Coredramon] from this card's security check, does this card check another Security card?
Yes, it gains ＜Security Attack +1＞ from its effect and updates its security attack value. You re-calculate its security attack and continue checking security based on its new security attack. (For more information see Attack Resolution)
asked about Azulongmon (BT6-029)
A Digimon that has this card in its digivolution cards attacks, and a security check was performed on my opponent's security stack. If the attacking Digimon with this card in its digivolution cards digivolves into a Digimon with ＜Security Attack +1＞ using this card's inherited effect, is another security check performed?
Yes, another security check is performed.
Ruled Apr 4, 2025 · asked about Gigimon (BT21-001)
This card attacks and I perform a security check on my opponent. If I then use this card's ＜Your Turn＞ effect to digivolve into a Digimon card with ＜Security Attack +1＞, is another security check performed?
Yes, another security check is performed.
Ruled Apr 4, 2025 · asked about BurningGreymon (BT21-014)
Can a card that has an "isn't affected by [...] effects" effect be given an effect?
Yes, it can. It won't be affected by it, but it can be given an effect. However, if an effect such as ＜Security Attack anti＞ is given to a Digimon that isn't affected by effects, the Digimon won't be considered to have that effect.
Ruled Apr 4, 2025 · asked about WarGreymon (ST20-11)
Rule text © Bandai, quoted from the official Comprehensive Rules for reference. Combalo is not affiliated with Bandai.
